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since the discovery of ( 1 ) ceres in 1801 @xcite the majority of observations of asteroids and other minor planets have been conducted in visible wavelengths . while visible light can provide very accurate positions , the interpretation of photometry is rendered ambiguous by the dependence of the observed flux on both the size and albedo of the asteroid . this relationship is described by the equation : @xmath1 ( see * ? ? ? * for an overview and references therein for its derivation ) , where @xmath2 is the diameter in kilometers , @xmath3 is the visible geometric albedo , and @xmath4 is the absolute magnitude which is defined as the apparent magnitude the body would have @xmath5au from the sun , @xmath5au from the observer , and at @xmath6 phase angle . albedos of solar system objects are observed to vary from only a few percent up to nearly @xmath7 percent for icy surfaces , causing diameters inferred from visible data alone to have nearly an order of magnitude uncertainty . multiwavelength visible surveys have found statistical correlations between the albedos and the visible colors of asteroids ( e.g. * ? ? ? * ) , however the accuracy of the mapping between these two properties for individual objects is currently being examined @xcite . using an independent method of measurement for either the albedo or the diameter allows for the unique solution of the other , given a visible @xmath4 value . accurate diameters and albedos for a large number of asteroids enable a number of important areas of research into the history and formation of the solar system . diameter measurements of asteroids based on infrared flux allow us to quantify the size - frequency distribution ( sfd ) of the bodies in a way independent of assumptions about the translation from h magnitude to diameter that are typically required . both the initial accretion and formation process of asteroids as well as the subsequent collisional and orbital evolution affect the current main belt sfd , and a well - measured sfd will allow us to put constraints on these processes . the albedo of an asteroid , meanwhile , is a strong function of its composition . compositional gradients for the main belt have been shown in the past from both infrared and spectral surveys ( e.g. * ? ? ? * ; * ? ? ? * ; * ? ? ? * ; * ? ? ? * ) , but only for a limited number of objects . a large survey conducted in mid - infrared wavelengths will allow main belt albedos and diameters to be produced with good accuracy ; this in turn will allow us to study the compositional gradient of the solar system and may ultimately allow us to set constraints on any major planetary migration that may have occurred . recent work has attempted to understand the sfd of asteroids as it relates to the impact physics dominating the evolution of the main belt with the aid of numerical simulations . @xcite analytically calculated the behavior of a population in a steady - state collisionally dominated regime to determine how the slope of a population s sfd behaved as a function of the mechanical strength of the material composing the body . they find that while a strength - less regime yields a nominal power - law slope of @xmath8 , including the strength of the body can vary the result over a range of slopes depending on the specific circumstances . expanding on this , @xcite simulated a variety of impacts with numerical hydrocodes to look for the effect of internal structure , impact angle , impact velocity , and impactor - target size ratio on the resultant sfd of the shattered products . these authors have also attempted to match their numerical results to measured sfds for asteroid families to determine the initial size of the parent body , however the data used have depended on assumptions for the albedos of the asteroids . for the larger main belt population , @xcite have modeled the evolution of various initial size distributions to determine what the current mba sfd can indicate about the sfd present at the formation of the asteroids . their results show a clear peak in formation sfd , with few objects smaller than @xmath9 km forming directly from the protosolar nebula , however these results are also based on diameters determined from assumed albedos . similarly , @xcite have investigated the sources and sinks of excited mbas and the effect orbital evolution has the sfd of the main belt . studies of asteroid albedo distributions have in the past been limited by small data sets . early measurements were made using thermal infrared detectors on ground - based telescopes to determine radiometric diameters and thus albedos for tens of objects ( e.g. * ? ? ? * ) . the _ infrared astronomical satellite _ ( iras ) revolutionized studies of physical properties of the main belt by observing over @xmath10 asteroids in the thermal infrared , determining albedos and diameters for these bodies in a uniform way @xcite . to date , iras represents the largest and most complete survey of asteroid albedos in the literature . if the sizes and albedos of the members of an asteroid family are known , it is possible to use their orbital evolution to study their age . the yarkovsky effect ( see * ? ? ? * for a review of the subject ) occurs when incident optical light is absorbed and re - emitted as thermal infrared photons in a different direction , usually due to the rotation of the body . this difference in momentum causes changes in the orbit of the body over long time intervals . @xcite use this effect to refine predictions for the age of the karin family based on backwards integration of orbital parameters . as karin is one of the youngest families @xcite this effect becomes increasingly important for accurate age - dating of families the older they are . the accuracy of this technique , however , depends on knowing sizes and albedos of the objects to a high degree of certainty . the distribution of albedos in the main belt as a whole and broken down by region can provide us a window into the changing chemical and mineralogical processes active in different regions of the early solar system . although the current understanding of the history of the main belt has the asteroids forming in or near their current locations , new theories are being proposed that the main belt may in fact be the result of a mixing of two distinct populations from different regions of the solar system . migrations of the giant planets may have both cleared many of the objects that initially formed in the main belt region and repopulated this area with objects from beyond the `` snow line '' @xcite . we then might expect the main belt to be composed of two overlapping populations , one having formed in a volatile - poor region of the protosolar disk and one forming in a volatile rich area , though the latter population would lose any surface volatiles over the age of the solar system . under this scenario albedo may be able to trace dynamical evolution as well as chemical processing . there are very few ways to measure the albedo of an asteroid directly . observations taken _ in situ _ by spacecraft can be used to measure both the absolute albedo and its variation across a body s surface ( e.g. * ? ? ? * ) , as well as its diameter , though only a handful of objects have been visited by spacecraft . imaging polarimetry can also be used to determine the integrated surface albedo for a number of objects @xcite , but appropriately calibrated instrumentation is uncommon . similarly , direct measurements of asteroid diameters can come from a variety of techniques . resolved imaging of an asteroid provides the simplest method of size determination , however the use of e.g. _ hst _ or keck adaptive optics ( ao ) only allows the largest few asteroids to be resolved ( e.g. * ? ? ? * ; * ? ? ? asteroid occultations of background stars also provide a robust method of diameter measurement @xcite , however the logistical constraints of occultation events make obtaining a large sample difficult , and shape measurements are only instantaneous projections . radar measurements can provide precise distances , rotation rates , projected profiles , and with sufficient data 3d shape models @xcite , but returned fluxes fall off quickly with distance which limits the number of objects observable with this technique . indirect measurements of asteroid diameters and albedos can provide a wealth of information both for individual objects and the population as a whole . these techniques typically can observe a large number of objects in a relatively short period of time , provide uniform data for an entire population , and have understood biases that allow for determination of the true , underlying distributions . careful calibration of indirect measurements is required , but once established these techniques can provide highly accurate measurements of asteroid physical properties for a large number of bodies .    for objects that have known orbits , measurement of the infrared flux emitted from the surface can be used to constrain the diameter of the body ( see  [ sec.models ] for a discussion of the method used here ) . infrared imaging can be accomplished rapidly when integrated in an all - sky survey . thermal infrared measurements of a large sample of asteroids represent the best way to determine robust diameters rapidly for many thousands of objects . in this paper , we present preliminary results from the _ wide - field infrared survey explorer _ ( wise ) space telescope , the next - generation all - sky infrared survey , focusing here on the cryogenic observations of main belt asteroids . launched on 2009 december 14 , wise is a thermal infrared space telescope that performed an all - sky survey from 2010 january 14 until it exhausted the telescope - cooling hydrogen ice on 2010 august 5 . the survey continued during the warmup of this secondary tank with limited sensitivity in the longer wavelengths until the primary coolant , responsible for maintaining detector temperature , exhausted 2010 october 1 . wise subsequently entered a post - cryogenic mission to complete the survey of the largest mbas , continue discovering new neos , and complete a second - pass survey of the inertial sky in the two shortest wavelengths . during its cryogenic mission , wise imaged the sky in four infrared wavelengths simultaneously using dichroic beamsplitters to produce co - boresight images with band centers at @xmath11 m , @xmath12 m , @xmath13 m and @xmath14 m ( w1 , w2 , w3 , and w4 , respectively ) . the latter two bands are particularly important for solar system studies as the dominant amount of the flux received from asteroids is from thermal emission peaking at these wavelengths . first - pass calibration of the wise data was tuned to the fully cryogenic mission and while the final calibration currently being undertaken will finalize measurements obtained during each warm - up stage , we restrict our current analysis to objects observed during this fully cryogenic stage . pre - launch descriptions of wise were given by @xcite and @xcite , while post - launch overviews , including initial calibrations and color corrections , are presented by @xcite and @xcite . the wise survey follows a continuous scan along lines of ecliptic longitude at a solar elongation of @xmath15 as the spacecraft orbits above the terminator of the earth . an oscillating scan mirror compensates for this motion , providing stable images with effective integration times of @xmath16seconds . the positions of all known minor planets are propagated to the time of each observation and checked against all transient sources in the field of view , recording the appropriate calibrated magnitudes if observed . in this way , thermal measurements of each minor planet cataloged by the minor planet center ( mpc ) can be found . in addition to previously known objects , the wise processing pipeline includes the capability to discover new objects via the neowise enhancement @xcite . while comprehensive followup of new potential near - earth objects ( neos ) has been one of the priorities of the wise team @xcite , the large number of main belt discoveries ( @xmath17 ) has prohibited sufficient immediate ground - based followup . large - scale asteroid surveys such as spacewatch and the catalina sky survey have already provided serendipitous followup of many of the new wise mbas and will continue to do so , while future surveys are expected to recover the remainder . as described in @xcite and @xcite , the wise cadence resulted in an average of 10 - 12 observations of each minor planet detected over @xmath18hours . for a subset of the main belt , predominantly in the outer regions , observations were obtained at two or more epochs depending on the relative motion of the object and earth around the sun .      in this paper , we consider only those main belt asteroids detected by neowise / wmops during the cryogenic portion of the mission , shown in a top - down view of the inner solar system in fig  [ fig.pacman ] . this consists of @xmath19 unique objects . we obtained our data used for fitting in a method identical to the one described in @xcite and @xcite , though tuned for mbas . specifically , we queried the minor planet center observation file for all observations submitted from wise ( observatory code c51 ) . we then used the resultant ra - dec - time values as input for a query of the wise individual exposure archive , the `` level 1b '' data , through the gator tool provided by the infrared science archive ( irsa ) . to ensure that only the observations of the moving objects were returned , we restricted our search radius to 0.3 arcsecs from the position and 2 seconds from the time obtained for the detection from the mpc . additionally , we set a constraint of jd@xmath20 to ensure that only data during the fully cryogenic mission was used for this initial survey . this method of data acquisition has the benefit of ensuring all observations used have been vetted both internally by the wise data pipeline and again by the mpc . all data were processed using the first pass version of the wise pipeline , which computed dark current / sky offset levels , flagged instrumental artifacts such as latent images and diffraction spikes and performed linearity compensation . only observations with an artifact flag cc_flags@xmath21 or @xmath22 in a band were accepted : a value of @xmath23 indicates no evidence of artifact was found by the pipeline , while @xmath22 indicates the possibility of contamination by a latent image . as discussed in @xcite we find that the pipeline was overly conservative in artifact flagging and cc_flags@xmath24 values have similar fluxes to cc_flags@xmath21 detections while increasing the number of usable observations by @xmath25 . the ph_qual flag was required to have a value of a , b or c to again ensure only valid detections were used . non - linearity and saturation are a particular concern for the brightest mbas , especially in bands w3 and w4 . the wise data reduction pipeline applies a non - linearity and saturation correction for all observations brighter than the threshold of @xmath26  mag , @xmath27  mag , @xmath28  mag , @xmath29  mag . objects with magnitudes brighter than @xmath30 and @xmath31 were assigned errors of @xmath32mag to account for the change in the point - spread function for very bright objects , and a linear correction to the magnitudes of sources with @xmath33 was applied @xcite . following those authors , we did not use objects brighter than @xmath34 and @xmath35 for thermal modeling . each object was required to have been observed at least 3 times in one wise band with magnitude error @xmath36 to undergo thermal modeling , as a precaution against contamination by spurious sources ( e.g. background noise , cosmic rays , stars , etc . ) . for multiple - band thermal models we required other bands to have at least @xmath37 of the detection rate of the band with the largest number of detections , usually w3 for mbas . to reduce the possibility of confusion with inertially fixed sources such as stars and galaxies , we searched each position retrieved from the level 1b catalog in the daily and atlas coadded catalogs ( also served by irsa ) within 6.5 arcsecs , equivalent to the w1 , w2 and w3 beam sizes . these searches looked for sources that appeared at least twice and in at least @xmath38 of the images covering that location . any sources returned from these searches were considered to be inertial , which could contaminate the observation of the asteroid at that position . thus that asteroid detection was discarded from the thermal modeling routine .    in fig  [ fig.colors ] we show the mean colors of inner solar system objects as observed during the cryogenic phase of the wise mission with the mbas highlighted in black ( see * ? ? ? * ; * ? ? ? * for discussions on the other populations shown in this figure ) . the bifurcation in the w1-w2 color observed for the mbas traces the two dominant albedo groupings in the main belt ( see below for further discussion ) . the mbas span a wide range of colors and are bounded by the neo and jupiter trojan populations . note that mbas occupying color - space typically associated with one of the other populations are candidates for objects that may have been misidentified as mbas during preliminary orbit fitting . we show in fig  [ fig.colordist ] the color for each object as a function of heliocentric distance at the time of observation . color , especially in bands dominated by thermal emission , is a strong function of temperature of the body and thus distance from the sun . figure  [ fig.velocity ] shows the sky - plane velocity for each object compared with its w3-w4 color . the mean sky - plane velocity for mbas is @xmath32deg / day ; objects with velocities significantly larger than this are candidates for neos misclassified as mbas , requiring further followup . future work will combine color and sky - plane velocity cuts to distinguish mbas with poorly known orbits from neos and trojans . in contrast to the visible flux received from an asteroid , which is reflected sunlight , the mid - ir flux beyond @xmath39 m from an object in the main belt is almost completely thermal emission from that body . for an object with an established orbit , the phase angle and distances to the asteroid from the earth and the sun are well known , thus the observed thermal flux can be converted into a total emitted flux at the surface . by making assumptions for some physical surface properties , a diameter can be computed from a single band detection . when simultaneous thermal measurements at multiple wavelengths are available the beaming parameter of the surface material may also be fit to the data . the beaming parameter ( @xmath40 ) represents the deviation of the thermal emission from that of a smooth non - rotating sphere due to rotation and surface roughness , and is used to consolidate the uncertainty in the values of the surface thermal properties , including emissivity . when visible - light data are additionally available , the visible albedo ( @xmath3 ) becomes a free parameter that can now also be fit using the two data sets in conjunction . further data such as w1 or w2 measurements that are dominated by reflected sunlight allow us to derive an independent measure of the ratio of visible to nir reflectance as well .    in order to analyze the thermal infrared asteroid measurements from the iras satellite , @xcite developed the `` standard thermal model '' ( stm ) for asteroids , calibrated against measurements from ( 1 ) ceres and ( 2 ) pallas . in this model , the beaming parameter was held constant to @xmath41 based on the ground - truth occultation observations of the calibrator asteroids . subsequent work indicated that this model might not be appropriate for smaller asteroids , thus @xcite modified stm to a form appropriate for a `` near - earth asteroid thermal model '' ( neatm ) , where @xmath40 is allowed to vary . while designed specifically to account for the breakdown of stm when considering neos , neatm can be applied quite readily to a wide range of bodies in the solar system ( e.g. * ? ? ? * ; * ? ? ? * ) . @xcite compared neatm with a full thermophysical model of a cratered surface and found that for low phases both models produce consistent results . @xcite present an investigation of objects with a beaming parameter at the theoretical maximum of @xmath42 which occurs for a body rotating so quickly it is latitudinally isothermal . we have performed preliminary thermal modeling of mbas based on the wise first - pass data processing pipeline described above , covering observations taken during the cryogenic phase of the mission . we modeled each object as a non - rotating sphere with triangular facets and variable diameter , beaming parameter , visible albedo , and nir reflectance ratio as appropriate for the data . relative distances and phase angles were computed for each measurement to ensure changing distances do not bias the resultant fits . although we do not expect all , or even most , asteroids to have a spherical shape , our observations covering @xmath18hours smooth out rotation effects and allow us to determine the effective diameter of a spherical body with the same physical properties . long period rotators ( @xmath43days ) with large amplitudes , e.g. binary asteroids with mass fraction @xmath44 , will have poor fits resulting in a moderate mis - measurement of albedo and diameter . future work will address the light curve component of our data set to determine the minimum and maximum sizes of our targets in order to estimate first - order shape models as well as estimates of the fraction of binaries in the main belt .    at each instance , the temperature on every facet was computed and color corrected based on the values in @xcite . the emitted thermal flux for each facet was computed with the neatm model and night - side facets were assumed to contribute zero flux . a reflected light model was used to determine the reflected component in each band for all illuminated facets visible to wise at the time of observation ; this was most important for w1 and w2 . the model reflected and emitted light was summed for all facets and converted to a model magnitude using the jansky flux of a zero magnitude source provided in @xcite and modified according to the text for red sources : @xmath45jy for w1 , @xmath46jy for w2 , @xmath47jy for w3 and @xmath48jy for w4 . note that the modifications in the w3 and w4 zeropoints are the result of adjusting the central wavelengths of these bands to @xmath49 m and @xmath50 m to correct the discrepancy observed in the calibration tests between blue - spectrum and red - spectrum objects . these model magnitudes were then compared with the measured magnitudes , and the model was iterated through a least - squares fitting routine until the best fit was found .    for objects with two thermally dominated bands , the beaming parameter was allowed to vary , while for those with only one thermal band we used a fixed value of @xmath51 , based on the peak of the @xmath40 distribution of mbas that were fit with a variable beaming parameter ( see below ) . for objects where no detected band was dominated ( @xmath52 ) by reflected light we assumed a nir reflectance ratio of @xmath53 as was found for mbas with fitted nir reflectances ( see below ) . these objects typically were not detected in w1 and either were not detected or had both thermal emission and reflected light in w2 . monte carlo simulations were performed in each case to determine the errors on all variable parameters . for high s / n cases where the quoted error on the measured magnitude only represented the statistical error , we set a floor of @xmath54 , representing the absolute error on the photometry @xcite . for all objects we assumed that the emissivity @xmath55 and we assumed that the magnitude - phase slope parameter ( c.f . * ? * ) was @xmath56 unless otherwise given by the mpc or in the lightcurve database ( lcdb , * ? ? ? * ) . the quoted errors on the modeled parameters are equal to the weighted standard deviation of all monte carlo trial values . for objects with fixed beaming parameter , an error of @xmath57 was assumed to allow for proper error determination of derived parameters based on the mean and standard deviation of all best - fitting beaming parameters for objects with fitted values ( see  [ sec.etavar ] ) . similarly , for objects with fixed ir reflectance ratios , we assume an error bar of @xmath58 based on the mean and standard deviation of objects with fitted ir reflectance ratios ( see  [ sec.ratio ] ) . we note that as the flux calibrations presented by @xcite set a limit on the computed diameter accuracy for sources in the wise data of @xmath59 . this error implies a minimum fractional error for albedo of @xmath60 assuming a perfect h magnitude . these values are in addition to any poissonian error inherent to the observations , though for most of the objects presented here the calibration errors dominate our solutions .    in total @xmath19 main belt asteroids , selected from the cryogenic phase of the survey , had sufficient number and quality of detections to allow us to perform thermal modeling and determine their effective diameter . of these , @xmath61 objects had orbital arcs shorter than @xmath62 days ; as such their orbits have a larger uncertainty than the rest of the population , which corresponds to uncertainty in their geocentric and heliocentric distances , which will naturally increase the error on their calculated diameters . additionally , @xmath63 objects also had available optical data allowing us to calculate albedo as well as diameter . both of these latter two populations are changing continuously , as ground - based surveys submit serendipidous visible observations of neowise - discovered asteroids ( allowing us to fit albedos and allowing the mpc to fit better orbits ) , and as the mpc links wise observations with previous one - night stands and lost asteroids . we provide a table of our best fits for main belt asteroids from the pass 1 processed cryogenic survey data online at : _ / staff / bauer / neowise_pass1/_. this table contains : the mpc - packed format name of the object ; the @xmath4 and @xmath64 values used ; the diameter , albedo , beaming parameter , and infrared albedo as well as associated error bars ; the number of observations in each wise band that were used for fitting ; and the mean modified julian date of the observations . for objects observed at multiple epochs with fits consistent across all observations , each epoch is presented as a separate row in the table . as discussed in [ sec.unusual ] objects where multiple epochs were forced to fit to a single model because the separate fits were divergent are presented as a single row . objects without optical data at the time of publication have `` nan '' ( `` not a number '' ) values for absolute magnitude and albedo . similarly , objects for which an infrared albedo could not be fit nor had literature optical data that could be used with an assumed reflectance ratio to estimate an infrared albedo ( see  [ sec.ratio ] ) have `` nan '' values in this entry . using fluxes from the wise data , and a faceted neatm model , we are able to determine diameters for our observed objects . in fig  [ fig.dcum ] we show the cumulative preliminary raw size - frequency distribution ( prsfd ) for the three major regions of the main belt : the inner - main belt ( imb , those objects with @xmath65au @xmath66au ) , the middle - main belt ( mmb , objects with @xmath67au @xmath68au ) , and the outer - main belt ( omb , objects with @xmath69au @xmath70au ) . in all cases , perihelion distance was required to be beyond the orbit of mars , @xmath71au . also plotted on the distribution histograms are 100-trial monte carlo ( mc ) simulations of the diameter distribution including the appropriate measured errors . this mean mc distribution and associated error are shown as points ; the error bar sizes are smaller than the point size . we see no significiant change between the mc distribution from the distribution of best - fit diameters . we find the slope of the prsfd for smaller objects in all three subpopulations to be consistent with the @xmath72 value found by @xcite , however debiasing will be critical to determining the true value of this slope . we observe a significant change in slope for the prsfd between @xmath73 km , consistent with the location of the `` kink '' seen in the debiased @xmath4 distribution by @xcite . a debiasing campaign of the observed population currently underway will allow us to explore the true sfds of the populations and will be discussed in future work . for objects with detections in at least two thermal bands , we allow the beaming parameter to vary during the thermal model fitting . we are able to fit beaming parameters for @xmath74 mbas . we find a wide range of best - fit beaming parameters between the theoretical limits of @xmath75 and @xmath76 , with a peak value of @xmath51 and standard deviation of @xmath57 . in fig  [ fig.etascat ] we show the beaming parameter found for all objects with fitted values as a function of a variety of orbital and physical parameters . beaming parameter has a weak dependence on semi - major axis ( fig  [ fig.etascat]a ) , an effect that is more pronounced for the relationship with phase angle ( fig  [ fig.etascat]g ) . note that due to the constraints of the pointing of wise over the course of the survey to solar elongations @xmath77 , phase angle , heliocentric distance and geocentric distance are strongly correlated , though ecliptic latitude of the observations as well small changes in the exact pointing over the survey weaken this relation . @xcite has shown that for the phase angles we typically observe mbas at ( @xmath78 ) the differences in calculated diameter and beaming parameter between neatm and more realistic thermophysical models is minimal over a large range of observing geometries . from the raw distribution , the beaming parameter shows no dependence on size ( fig  [ fig.etascat]b ) , eccentricity ( fig  [ fig.etascat]c ) , inclination ( fig  [ fig.etascat]d ) or absolute magnitude ( fig  [ fig.etascat]e ) . we find a best - fit linear relation to the running average of beaming parameter as a function of phase of : @xmath79 where @xmath40 is the beaming parameter and @xmath80 is the phase angle in degrees . this is consistent with the results found in @xcite for the neos from wise , but differs significantly from the results of @xcite who found a best - fitting line of @xmath81 . for phase angles within the main belt ( @xmath82 ) the average beaming ranges from @xmath83 although the spread around this value is large . thus @xmath84 for objects with only a single thermal band is a reasonable assumption for objects in the main belt . debiasing will allow us to account for any detection - limit effects that may bias the selection of objects that have sufficient data for fitting of the beaming parameter . note that while the running average over the beaming parameter shows a dependence on albedo ( fig  [ fig.etascat]f ) and subsolar temperature ( fig  [ fig.etascat]h ) , albedo determinations are very sensitive to survey biases , both from wise and optical followup , while subsolar temperature is a function of beaming parameter as per the equation from the definition of neatm in @xcite : @xmath85^{0.25 } \label{eq.tss}\ ] ] ( where @xmath86 is the subsolar temperature , @xmath87 is the bond albedo , @xmath88 the incident solar flux , @xmath40 the beaming parameter , @xmath89 the emissivity , and @xmath90 the stefan - boltzmann constant ) , and so this can not be used as an independent constraint . object - wide bins stepped by @xmath91 objects . the picket - fence effect in the absolute magnitude is an artifact of the @xmath92mag reported precision of @xmath4 for most objects . ] we show in fig  [ fig.etahist ] histograms of the beaming parameter distribution for the inner- , middle- , and outer - main belt populations . also shown as points are the mean distribution and error from a 100-trial monte carlo simulation of the distribution using the error bar on each fitted beaming parameter . all populations show longer tails toward higher values of beaming parameter than toward lower , and have consistent shapes . the shift in peak beaming parameter with phase can be seen as the change in distribution between populations with different average phase angles . with the inclusion of visible data in our modeling , we determine albedos as well as diameters for the asteroids discussed here . we use the published @xmath4 and @xmath64 values for all asteroids , available from the mpc . during the confirmation of the calibration of wise for asteroids , @xcite investigated the need for an offset in h to account for systematic errors in h values , but found that no offset was required ( c.f . * who found a @xmath32mag shift ) . the @xmath4 magnitudes were assigned a random error of @xmath93mag . we perform monte carlo simulations of our visible light measurements as well as of the thermal measurements to quantify the error on albedo , however in all cases the minimum error on albedo will be @xmath94 @xcite for objects with optical data and one good thermal band . we have sufficient optical data to determine albedos for @xmath63 mbas . though our individual albedos have large error bars , the population statistics can still provide us with a window into the state of the surface composition of the main belt .        in fig  [ fig.alball ] we show the differential preliminary raw albedo distribution ( prad ) of all the inner- , middle- , and outer - main belt asteroids in our survey . we then take the fitted albedos and their respective error bars and perform a 100-trial mc simulation of these values to find a mean distribution with errors , shown as points . in all cases , the peaks of the distributions broaden slightly in the mc simulation , which is expected . in log - albedo - space the differential distribution is well described by a bimodal gaussian distribution . we show our best - fitting double - gaussian ( fitted to the mean distribution found through the mc simulations ) as the smooth dotted curve under each set of points . the bimodality in albedo likely traces the difference between the two major branches of asteroid composition : the s - type asteroids with high albedos and the c - type asteroids with low albedos @xcite . @xcite investigate the specific link between albedo and a variety of taxonomic classification systems . as discussed above , however , the prad will naturally include the observational biases of the ground - based telescopes used to determine the optical magnitudes needed to find the visible albedo , favoring higher albedo asteroids and over - representing their contribution to the total population , particularly in the inner main belt . debiasing , currently being undertaken , will allow us to quantify and remove this effect . the mean value and width of the gaussian that best describes the dark peak of the prad for each population is consistent across populations , with mean albedo @xmath95 and a dispersion of @xmath96 . note that the gaussian error bars on the @xmath97 value are in log space , and thus asymmetric in native units . unlike the dark asteroids , the bright complex shows a distinct change in the mean value in the prad as one moves out in the main belt . the mean albedo of the bright peak for the gaussian describing each population is : @xmath98 , @xmath99 , and @xmath100 , with widths of @xmath101 , @xmath102 , and @xmath103 . the objects discovered by neowise that have not had optical followup will add a significant bias to the prad as these objects are most likely to be ones missed by optical surveys , i.e. lower albedo asteroids . during the cryogenic portion of the survey , neowise observed @xmath104 previously unknown main belt asteroids with data of sufficient quality for thermal modeling and with orbital arcs longer than @xmath105 day ( and thus not considered `` one night stand '' observations by the mpc ) . some @xmath106 additional asteroids were given temporary designations by the mpc but did not have sufficient arc length to calculate an orbit . while they do not have known orbits and thus ca nt be classified as members of the main belt or not , we can use this to set an upper limit on the number of lost mbas . as these objects are linked to older precovery data or are serendipitously followed up our count of discovered objects with computed orbits will increase . out of these discovered objects @xmath107 have optical photometric data as well as thermal infrared , allowing for albedo determination . it should be noted that while many of the discovered objects have optical observations , there is a strong bias in favor of recovery of the highest albedo discoveries by subsequent ground based observations . the visible light received from an object is directly proportional to the albedo of that object , while the thermal infrared flux is driven by the temperature of the surface , which is only weakly dependent on albedo as shown in eq  [ eq.tss ] . as such , optical surveys show a significant albedo bias towards brighter objects for both discovery and recovery observations , while the neowise infrared survey is more sensitive to detection of low albedo objects . any survey will have inherent biases in the data set and it is necessary to account for them before the true albedo distribution can be determined for a population .    , but for only the neowise - discovered mbas that also received optical photometric followup . ]    we show in fig  [ fig.discalb ] the albedo distribution of the neowise - discovered mbas with optical photometry for the inner- , middle- , and outer - belt subpopulations . even though the optical followup will be biased toward favoring higher albedo objects , the neowise discoveries are dominated by low albedos , as these are the objects that were initially missed by the ground - based optical surveys . all three distributions can be described by a single gaussian function with mean albedo between @xmath108 and @xmath109 , consistent with the values found for the dark complex in the whole population above . we can use the albedos of the discovered objects and the roughly equal number of objects in each subgroup as an initial attempt to constrain the effect of these lost objects on the greater albedo distribution . we show in fig  [ fig.albwithlost ] a revised albedo distribution including this toy model for the albedos of the @xmath110 main belt asteroids without followup photometry , based on the albedo distribution of the neowise - discovered objects . as expected the primary effect is to increase the relative abundance of dark objects in each region of the belt . , but now including a simple model for the objects discovered by neowise that have no optical followup photometry . ] we note that the more detailed way to properly account for the uncertainties introduced by objects without follow - up and objects for which reliable orbits could not be determined is through careful modeling of survey biases . a debiased study of the main belt asteroids will be subject of future work , and will allow us to determine the true size and albedo distributions of these objects . we also investigate the distribution of albedo as a function of orbital parameters , in particular semimajor axis ( @xmath111 ) , eccentricity ( @xmath112 ) and inclination ( @xmath113 ) . figure  [ fig.apcolor ] shows the distribution of albedos as a function of semimajor axis . we have color - coded the points by albedo using a `` weather - map '' palette divided evenly in @xmath114 space , and use this same color code for all subsequent plots . dark colors ( black , grey , dark blue , blue ) indicate objects in the low albedo complex , while brighter colors ( magenta , red , orange , yellow ) indicate members of the high albedo complex . objects colored yellow have very high albedos and are concentrated in the hungaria region and inner - main belt near the orbit of ( 4 ) vesta . these largest albedos found are likely artifacts of using @xmath56 to calculate the @xmath4 value : while the thermal models for the diameters of these objects show no errors , using the literature @xmath4 value forces anomalously high albedos . we investigate the use of different @xmath4 and @xmath64 values for these highest albedo objects in a future publication . space and are used to denote albedo in subsequent plots . ] we show in figures  [ fig.aip ] and [ fig.aep ] the plot of semimajor axis vs. inclination and eccentricity , respectively , using the same colors denoted above . asteroid albedos are not homogeneously distributed throughout the main belt , but rather are clumped in a - e - i space , correlating with the positions of known asteroid families @xcite . mbas have been previously shown to cluster in color - space @xcite and show similar reflectance spectra ( e.g. * ? ? ? * ; * ? ? ? indicative of the common origin of members of families , which are the result of a catastrophic breakup of a single parent body @xcite . the clustering of albedos is a further confirmation of this origin . a future paper in this series will investigate the use of albedo as an added criterion to the orbital parameters typically used to determine family membership .    . the reflectance spectrum for most asteroids ( but not all , e.g. b - types ) show an increasing value as the wavelength moves from the visible to near - infrared ( nir ) region of the spectrum ( e.g. * ? ? ? * etc . ) . if these trends continue into the w1 and w2 bandpasses we would expect the reflectance observed there to be higher than observed in the optical . we assume in our thermal model that the reflectance in w1 and w2 is the same ; depending on the location and depth of absorption bands this may not be universally true , but this assumption provides a generic constraint from which we can identify interesting objects that do not follow this assumption . reflectance depends on both the albedo and the @xmath64 slope parameter , both of which can not be assumed to be wavelength independent . we do not have sufficient phase coverage to fit @xmath115 and thus disentangle its effect from that of @xmath116 , so we present only the nir reflectance ratio for objects in the main belt with sufficient signal in w1 and/or w2 to be able to fit this value , a total of @xmath117 objects . we show in fig  [ fig.ratioscat ] plots of the nir reflectance ratio compared to a range of physical and orbital parameters , as well as running averages for those distributions . all objects were detected in thermal emission , however only objects with sufficient reflected light were able to provide fitted nir reflectance ratios . as such objects with higher ir albedos will be more likely to have a fitted reflectance ratio ( this is comparable to the biases inherent in optical surveys ) . evidence of this is apparent in fig  [ fig.ratioscat]e , where the running average of the ratio climbs for objects with fainter @xmath4 values . we note that as the visible albedo @xmath3 is intricately linked with the nir / vis ratio it can not be considered an independent variable . the structure seen in the running average in fig  [ fig.ratioscat]f is expected to be heavily influenced by the debiasing of the main belt population currently being undertaken . future work @xcite will explore the connection between taxonomic types derived from spectroscopy and photometry and the ir reflectance ratio found in the wise data . object - wide bins stepped by @xmath118 objects . the picket - fence effect in the absolute magnitude is an artifact of the @xmath92mag accuracy of @xmath4 for most objects . ]    in fig  [ fig.ratiodist ] we show the raw differential distribution of nir reflectance ratios for the imb , mmb , and omb asteroids with fitted ratios . also shown are the mean distribution and associated errors derived from a 100-trial monte carlo simulation of all measured reflectance ratios . all three populations show a peak between @xmath119ratio@xmath120 while the running average vs. semi - major axis varies across the main belt from @xmath121ratio@xmath122 . this is consistent with the values found for the neos by @xcite . for objects without fitted nir reflectance ratios , we use the mean of all fitted values of @xmath53 and an error bar based on the associated standard deviation of @xmath58 for modeling purposes . asteroid families were first identified as groups of objects that clustered tightly in orbital element - space by @xcite nearly a century ago . subsequent work has confirmed that families originate from the catastrophic breakup of a single parent asteroid after an impact ( see * ? ? ? * for a recent review of the current state of the field ) . this single mineralogical origin causes families to cluster tightly not only when comparing orbital elements but also when investigating colors @xcite and reflectance spectra ( e.g. * ? ? ? * ; * ? ? ? * etc . ) . the sfd of asteroid family members can also act as a tracer of the physical properties of the original parent body and can even be used to constrain the impact velocity and angle @xcite . however , a major deficiency in models to date has been the lack of measured diameters for the family members , forcing these values to be assumed based on the apparent magnitude of the object . albedo measurements of the largest bodies in a family are often available from the iras data set @xcite and can be used to assume an albedo for all family members , but this can add a significant and systematic error to the diameters used , especially in the cases where families may be mixed or where the largest body in a family may not be associated with the other members ( e.g. * ? ? ? there are a number of methods that can be used to determine which asteroids are members of a given family . the hierarchical clustering method ( hcm , * ? ? ? * ) , a commonly used technique , takes the differences in velocities between the proper orbital elements of objects to reveal dynamical associations . @xcite used this method to identify @xmath123 families out of @xmath124 mbas with low inclinations . we use these @xmath123 families as the baseline for our analysis , selecting those objects that appear both in that list and in the wise observations . as all these objects were discovered by optical surveys , there will be an inherent bias in the albedos favoring brighter family members . future work will address this bias and explore the use of albedo in conjunction with dynamical orbital properties to identify members of asteroid families and to reject interloper objects .    of the @xmath123 families identified by @xcite we find that @xmath125 have more than @xmath126 members observed during the cryogenic wise mission . due to the limitations of proper orbital element calculations , high inclination objects are not included in the astdys list of proper orbital elements @xcite . as such , high inclination families are likewise not represented in the list of family members . we have , however , included in our analysis the pallas family , identified by nesvorny ( private communication ) through the same methods as the @xmath123 published families . we also include the asteroids located in the hungaria region ; while not canonically included in the list of dynamical families , recent work by @xcite and @xcite support the classification of objects near hungaria in orbital space as a true dynamical family . these two added groups bring our total considered population up to @xmath127 families . we show in fig  [ fig.aipfam ] the proper inclination against the proper semimajor axis for all objects identified as a member of one of the families considered here . note that for the hungaria and pallas families proper orbital elements were not available and so osculating elements were used . similarly , we show in fig  [ fig.aepfam ] the proper eccentricity against the proper semimajor axis . in both plots , we use the same color scheme as shown in fig  [ fig.apcolor ] . it is quite apparent in these plots that families characteristically have uniform albedos , however there are notable exceptions .    . ]    . ] we show in fig  [ fig.dcumfam ] the cumulative prsfd for each of the families observed during the wise survey , as well as monte carlo simulations of all distributions with appropriate error bars . without debiasing , the prsfd can not be assumed to represent the true size distribution of the entire family population , as neither the neowise - inherent biases nor the biases in family selection have been accounted for . approximately @xmath128 of these families show kinks at the large end of the distribution inconsistent with a simple power - law . as small number statistics dominate families especially at the largest sizes , and because wise did not survey the entire main belt before the exhaustion of cryogen , precise debiasing is required to confidently measure the shape of the true sfd , especially at the largest sizes for each family .        in fig  [ fig.albfam ] we show the normalized prad for each family , along with the monte carlo results for each distribution . as was evident in fig  [ fig.aipfam ] and fig  [ fig.aepfam ] most families show a single - peaked albedo distribution , however as mentioned above debiasing will be critical to proper interpretation of these distributions . about @xmath129 of families include a small population of objects with non - characteristic albedos ; these may be the result of an improper association of background objects into the family . however , another @xmath0 of families show significant mixing between two albedo types that can not be solely due to the intrusion of a few background objects . in particular the nysa - polana and tirela families show nearly parity between the low and high albedo objects in the preliminary raw distributions .    among the families with sufficient data for study were the karin and koronis families . the karin family is believed to be a very young family , with an age of @xmath130myr , that formed from the breakup of a member of the much older ( @xmath131gyr ) koronis family @xcite . we fit a gaussian to the observed family albedo distributions . we find that the karin family has a lower mean albedo from this fit ( @xmath132 ) than the koronis family ( @xmath133 ) where the error bars represent the width of the best - fit gaussian . @xcite gives an overview of space weathering effects , a process that is generally thought to darken and redden surfaces of atmosphereless bodies in the solar system . our result is in apparent contradiction with this hypothesis under the assumption that the compositions of both families are identical . it is possible that variations in the composition , the presence of interlopers , or differentiation of the proto - koronis parent body could result in this observation . this analysis will be strengthened by the identification of more neowise - observed family members ( there were @xmath134 identified members of the karin family and @xmath135 members of the koronis family in this data set ) and the acquisition of additional compositional information . we also observed @xmath136 asteroids that were identified as members of the baptistina family . @xcite postulate that a fragment from the breakup of the baptistina family was the impactor responsible for the k / t mass extinction event . however , these authors assumed an albedo for the family members of @xmath137 . we find that the best fitting gaussian to the baptistina family member albedos has a mean of @xmath138 where the error bar indicates the width of the gaussian distribution . the method of age determination used by @xcite depends on the albedo assumed , and the calculated age @xmath139 is proportional to albedo following @xmath140 . thus our measured albedo results in an age for the breakup approximately @xmath141 times younger than that found with the lower assumed albedo ( from @xmath142myr to @xmath143myr ) , reducing the likelihood that the baptistina breakup generated the k / t impactor ( c.f . * ) .    also of interest are the families that show characteristic albedos distinct from the distribution observed in the main belt in fig  [ fig.alball ] . for example , the eos and aeolia families have characteristic albedos that fall in between the two peaks of the mba albedos . standing out as an outlier is the hungaria family : while showing a fairly strong coherence in albedo within the family , that characteristic albedo is incredibly high ( see below ) . future work will investigate whether variations in the @xmath64 slope parameter used to compute the @xmath4 absolute magnitude ( and thus the reflected - light albedo ) from the assumed value of @xmath56 typically used could account for the very large albedos calculated in these preliminary results . but for the prad . monte carlo simulations of the distributions are plotted as grey points with error bars . the distributions have been normalized to unit area for easier comparison . ] a small fraction of our objects had fits that did not conform to the general trends seen for the population as a whole . these highly unusual fits may be caused by strange physical parameters , incorrect associated properties ( e.g. @xmath4 mag , orbital elements , etc ) , or a break - down of the neatm model . in any case , these objects warrant further inspection . the most obvious candidates for this category of unusual fits are the asteroids with very high visible geometric albedos ( @xmath144 ) . we find @xmath145 objects in our survey have computed albedos that fall into this range , mostly contained within the region of orbital element space occupied by the hungaria and vesta families ( out of @xmath146 objects found in the hungaria region and @xmath147 in the vesta family ) , implying a possible mineralogical origin .    the asteroid ( 434 ) hungaria , the lowest numbered member of its namesake region , has a relatively large albedo of @xmath148 which can be explained by a composition dominated by the iron - poor mineral enstatite however some of the observed spectral features may require contamination from a darker , external source @xcite . this may indicate that albedos can range larger than @xmath149 , but albedos significantly higher than this are likely suspect . visual inspection of the thermal model fits of these objects shows that these high albedos are not due to a failure of the thermal model . for those objects where ir reflectance factor could also be fitted , we find values typically with reflectance ratio@xmath150 , while the distribution of beaming parameters for these objects is similar to that of the general main belt population . if the @xmath4 or @xmath64 values for these objects were very far from the true values this could result in the unusual calculated albedos .    by increasing the error bar we assume for the @xmath4 value and setting the ir reflectance ratio to a constant value of ratio@xmath151 ( the average for mbas ) we are able to find good fits of objects with reflected light in w1 and/or w2 . under this assumption , these objects all return fits with albedos comparable to that of ( 434 ) hungaria . however all these cases require the @xmath4 magnitudes to be @xmath152mag fainter than the values given by the minor planet center . a mis - identification of @xmath4 could be a symptom of an improper assumption for the @xmath64 slope parameter . in particular if @xmath64 should be much larger ( e.g. equal to or greater than the value for ( 44 ) nysa of @xmath153 this would result in an @xmath4 value that was too bright by @xmath154mag or more , which would thus give an albedo that was a factor of @xmath155 too large . this can account for some , but not all , of our improbably high albedos . large light curve amplitudes may also contribute to an absolute magnitude that is too bright . future work will address these objects in detail . in addition to the high albedo objects , we find a very small number of objects with beaming parameters at or close to the theoretical limit of @xmath42 . while some of these fits can be rejected upon visual inspection e.g. because of a single bad point in w4 dragging the fit to higher beaming parameter , at least @xmath156 objects appear to be legitimate fits with beaming parameters indicative of latitudinally - isothermal surfaces , though none of the fits show any significant lightcurve variations . further investigation will be critical to determine if they show rapid rotation or very high thermal inertia needed to explain this beaming parameter . approximately @xmath157 mbas were observed by wise at two different epochs . we initially treated each epoch separately for fitting purposes , and in the majority of cases the fits were within the expected error of each other . for those that were nt , we recomputed the best fitting model using both epochs together and forcing the physical parameters to be identical . we find @xmath158 objects for which the two - epoch fits could not produce a good fit at one or both epochs . while some of these objects may have very long rotation periods(@xmath159days ) and thus different projected diameters between epochs , others do not appear to show any light curve variation during our observations and may be cases of objects showing a significant difference between the temperatures of the morning and afternoon hemispheres of the body . we also observe @xmath160 objects with peak - to - trough light curve variations larger than @xmath161mag in w3 and average magnitude measurement error smaller than @xmath162 after removing spurious measurements . as these are not fitted amplitudes they represent a minimum for the light curve amplitude for the body observed . an example of one of these objects , ( 61469 ) , is shown in fig  [ fig.lc ] . there are also many objects with amplitudes smaller than this cutoff with readily apparent rotational effects , too . a future work will investigate specific light curves to determine the period and amplitude of the objects .    , @xmath163 and @xmath164 shown in red , green and cyan ( top to bottom ) respectively . the dashed line shows the modeled magnitudes for the best - fitting sphere . the period of this asteroid is approximately @xmath165hr assuming a double - peaked lightcurve . ] we have presented an initial analysis of main belt asteroids detected by neowise during the cryogenic portion of the wise mission . with infrared fluxes of sufficient quality to determine diameters and albedos for @xmath19 mbas , we show the power and great potential contained in this dataset . these data allow us to probe the composition , structure , and history of the main belt in ways that were previously impossible .    for objects with thermal emission detected in two or more bands we allowed the beaming parameter to vary . we find a mean beaming parameter of @xmath166 however we do see evidence of a phase dependence for the beaming parameter , ranging from @xmath167 for low phases to @xmath168 for higher phases ( within the main belt ) . the best fit linear relation between beaming and phase is @xmath169 which is a much shallower relation than seen previously in @xcite , but consistent with @xcite which included the near earth objects with fitted beaming parameters as well .    as was observed in the iras data ( e.g. * ? ? ? * ; * ? ? ? * ; * ? ? ? * ) the albedos of main belt asteroids are strongly bimodal : a bright complex ( @xmath170 ) and the dark complex ( @xmath171 ) . we find both peaks to be well described by gaussian distributions in log - albedo space . we find that the reflectance of asteroids in the w1 and w2 bandpasses is typically larger than the albedo found in visible light . the best fit ratio of reflectance ranges from @xmath172 in the imb to @xmath173 in the omb however the spread of values is large , and the final distribution will depend strongly on the debiasing . we identify albedo clusters in @xmath174 space corresponding to the locations of asteroid families . albedo is another coherent property of dynamical families in addition to orbit @xcite , color @xcite and reflectance spectrum ( e.g. * ? ? ? * ; * ? ? ? * etc . ) . albedo can also be used to trace the halos of similar objects that surround some families ( e.g. vesta , eos , etc . * ) that may be evidence of a collisional breakup very early in the age of the solar system . using asteroids previously identified though hcm techniques to be members of collisional families we show that most , but not all , families have a characteristic albedo . critical to any interpretation of the observations presented here is a careful accounting of the biases in both the wise survey data as well as the optical data used to derive albedos . we are currently undertaking an extensive debiasing campaign with the goal of producing unbiased size and albedo distributions for the main belt . this will be the subject of the next paper in this series . j.r.m . was supported by an appointment to the nasa postdoctoral program at jpl , administered by oak ridge associated universities through a contract with nasa . thanks m. delb and m. mueller for providing access to their thermal modeling code which was helpful in early test cases . this publication makes use of data products from the wide - field infrared survey explorer , which is a joint project of the university of california , los angeles , and the jet propulsion laboratory / california institute of technology , funded by the national aeronautics and space administration . this publication also makes use of data products from neowise , which is a project of the jet propulsion laboratory / california institute of technology , funded by the planetary science division of the national aeronautics and space administration . this research has made use of the nasa / ipac infrared science archive , which is operated by the jet propulsion laboratory , california institute of technology , under contract with the national aeronautics and space administration . we thank the worldwide community of dedicated amateur and professional astronomers devoted to minor planet follow - up observations . we are deeply grateful for the outstanding contributions of all members of the wise and neowise teams . cutri , r.m . , wright , e.l . , conrow , t. , bauer , j. , benford , d. , brandenburg , h , dailey , j. , eisenhardt , p.r.m . et  al . _ , 2011 , _ http://wise2.ipac.caltech.edu/docs/release/prelim/expsup/wise_prelrel_toc.html _ juri , m. , ivezi , z. , lupton , r.h . , quinn , t. , tabachnik , s. , fan , x. , gunn , j.e . , hennessy , g.s . , knapp , g.r . , munn , j.a . , pier , j.r . , rockosi , c.m . , schneider , d.p . , brinkmann , j. , csabai , i. & fukugita , m. , 2002 , aj , 124 , 1776 . nesvorn , d. , bottke , w.f . , vokrouhlick , d. , morbidelli , a. & jedicke , r. , 2006a , asteroids , comets , meteors , proc . of the 229th symp . of the iau , daniela , l. , sylvio ferraz , m. , and angel , f.j . ( eds ) , cambridge university press , 289 . ostro , s.j . , hudson , r.s . , benner , l.a.m . , giorgini , j.d . , magri , c. , margot , j.l . & nolan , m.c . , 2002 , asteroids iii , w. f. bottke jr . , a. cellino , p. paolicchi , and r. p. binzel ( eds ) , university of arizona press , 151 . wright , e.l . , eisenhardt , p. , mainzer , a.k . , ressler , m.e . , cutri , r.m . , jarrett , t. , kirkpatrick , j.d . , padgett , d. , _ et  al . _ , 2010 , aj , 140 , 1868 . zappal , v. , cellino , a. , farinella , p. & knezevic , z. , 1990 , aj , 100 , 2030 .
we present initial results from the wide - field infrared survey explorer ( wise ) , a four - band all - sky thermal infrared survey that produces data well suited to measuring the physical properties of asteroids , and the neowise enhancement to the wise mission allowing for detailed study of solar system objects . using a neatm thermal model fitting routine we compute diameters for over 100,000 main belt asteroids from their ir thermal flux , with errors better than @xmath0 . 
 we then incorporate literature values of visible measurements ( in the form of the h absolute magnitude ) to determine albedos . using these data 
 we investigate the albedo and diameter distributions of the main belt . 
 as observed previously , we find a change in the average albedo when comparing the inner , middle , and outer portions of the main belt . 
 we also confirm that the albedo distribution of each region is strongly bimodal . 
 we observe groupings of objects with similar albedos in regions of the main belt associated with dynamical breakup families . 
 asteroid families typically show a characteristic albedo for all members , but there are notable exceptions to this . 
 this paper is the first look at the main belt asteroids in the wise data , and only represents the preliminary , observed raw size and albedo distributions for the populations considered . 
 these distributions are subject to survey biases inherent to the neowise dataset and can not yet be interpreted as describing the true populations ; the debiased size and albedo distributions will be the subject of the next paper in this series .