The arrest of Serkan Golge -- who took US citizenship in 2010 and has worked for NASA in Houston since 2013 -- is just one of a number of incidents that have caused relations between Washington and Ankara to deteriorate sharply in recent years.

US consulate staff, journalists and even an American pastor have all been detained, accused of having ties with Turkish preacher Fethullah Gulen, who is in exile in the US and whose extradition Ankara has requested over his alleged role in the failed July 2016 coup against President Recep Tayyip Erdogan.

Pastor Andrew Brunson was released in October 2018.

Golge, 39, was initially sentenced to 7.5 years in prison in July 2016, but then saw it reduced to five years before finally being released on probation last week.

In an interview at his parents' home in Antakya, southern Turkey, he said people tended to believe there must be something to the charges if a NASA scientist is detained for so long.

But "I will give you an answer straight out: there was nothing," he insisted.

Golge said he was arrested on an "anonymous tip", of which there were many in the months following the coup attempt.

Vowing to take his case to both Turkey's Constitutional Court and the European Court of Human Rights, Golge pledged to "do whatever I have to do to fulfil my obligations" in the meantime.

These included reporting to police four days a week and not leaving Antakya.

Nevertheless, the scientist is hoping that the restrictions will be lifted so that he can "go back to the US and get back to my work" as part of a team studying the impact of space radiation on astronauts.

- Scarred for life -

Golge said his release on May 29 came shortly after a telephone conversation between Erdogan and US President Donald Trump.

He learned about it at 6:00 pm or 7:00 pm and it all "happened in 15-to-20 minutes," he said.

He was not allowed to call a taxi or his relatives from the prison, so he walked to the nearest village, where he called his mother to ask her to come and collect him.

Golge said he was kept in isolation and only allowed out of his cell for an hour a day.

The ordeal left both him and his family scarred forever, not to mention the devastating impact it had on their financial situation.

Golge said his wife became so pale and thin during the first weeks after his arrest that he barely recognised her when she visited.

It also deeply affected his sons, now aged three and eight, who came to fear that their father would never be released, Golge said.

His youngest son was only three months old when Golge was arrested.

"He calls me 'Dad' but he doesn't know me that well", he said.

"They say time heals most of the things... but I don't believe that. I think it heals most of the things but some of the things we experienced will stay with us forever."