Operated for the HM Coastguard by Bristow Helicopters Limited, the crews took over a role previously carried out by the RAF and Royal Navy.
The 500 missions include rescues of hillwalkers and climbers and searches for missing people.
The Inverness base is one of the UK's busiest search and rescue units.

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24 June 2015 Last updated at 13:21 BST
59-year-old Vivian Gabb, a pilates and tennis coach from London, was in the final stages of buying a house when the scammers struck.
She was unaware that her email had been hacked and every email she wrote and received was being monitored by criminals.
They sent her a message disguised as a follow-up email from her solicitor, asking for nearly £50,000 to be paid into their account.
The internet safety advice website Get Safe Online says more than half (51%) of people in the UK have been a victim of an online crime, and 15% of people have been victims of either attempted or successful hacks of their email account.
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Search and rescue helicopter crews based at Inverness Airport have completed 500 missions since the start of their duties in April last year.
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A woman has told the  Victoria Derbyshire programme how she was conned out of her life savings by scammers who sent her a 'phishing' email.