, show the father of two posing for the camera at work as a welder wearing a hard hat.
Prosecutors allege Rivera became involved with the plot to kill Trump after he was already involved in the plot to kill Alinejad.
Rivera had been brought on board by Farhad Shakeri - who the Department of Justice say was a middleman for the Iranian Revolutionary Guard.
Shakeri fled the US and is now hiding in Tehran, but Rivera was arrested by the FBI.
Rivera, who knew Shakeri from prison, allegedly roped in his pal Jonathon Loadholt, 36, of Staten Island, to help with the planned hit.
Prosecutors say Shakeri had already hired Rivera when his Iranian handlers decided to change tack and target Trump.
Rivera was allegedly tailing the Iranian journalist Alinejad and was waiting on a $100,000 (£80,000) payment before trying to kill her.
Alinejad is a prominent critic of Iran and released a video response to news of the assassination saying she was "shocked".
She said: "I know the nature of the Islamic Republic, to kill anyone who dare to challenge them, who criticised the Islamic ideology.
Watch unprecedented behind-the-scenes vid from winning Trump campaign as Don sips Coke & dictates fiery posts on Harris"Whatever I do makes them hurts them really bad that makes them want to kill me."
While attempting to find her, Shakeri, Loadholt and Rivera shared messages and photos - which were then provided to the Manhattan court by the FBI.
Prosecutors say that in February, Rivera and Loadholt traded texts and voice messages about Alinejad's habits with Rivera also parking outside her home and surveilling her.
In one voice note, Shakeri told Rivera that their target spent most of her time in specific rooms as he allegedly described getting into her home and killing her.
Rivera allegedly said: "You just gotta have patience to catch her either going in the house or coming out, or following her out somewhere and taking care of it. Don’t think about going in. In is a suicide move."
In another note Rivera said: "This b***h is hard to catch, bro. And because she hard to catch, there ain’t gonna be no simple pull up, unless there’s the luck of the draw."
Shakeri told the FBI he met a senior member of the Revolutionary Guard through his work in Tehran in the "oil and fuel businesses".
That was was known as Majid Soleimani but it is unknown if he was related to the former Iranian general.
Shakeri told the law enforcement agency that by late September, the Iranian had told him to put aside Alinejad and focus on surveilling, and ultimately assassinating, Trump.
The Iranians told Shakeri to devise a seven-day plan to spy on and murder Trump.
They appeared in a New York court on Thursday and a judge remanded Rivera and Loadholt in custody pending a criminal trial.
They also face counts of money laundering conspiracy, which could lead to 20 years in prison, and conspiracy to commit murder-for-hire.
Revealing the decision to charge Shakeri, Attorney General Merrick Garland said last night: “There are few actors in the world that pose as grave a threat to the national security of the US as does Iran.
“The Justice Department has charged an asset of the Iranian regime who was tasked by the regime to direct a network of criminal associates to further Iran’s assassination plots against its targets, including President-elect Donald Trump.”
FBI chief Christopher Wray said: "The Islamic Revolutionary Guard Corps has been conspiring with criminals and hitmen to target and gun down Americans on US soil, and that simply won’t be tolerated.
"Thanks to the hard work of the FBI, their deadly schemes were disrupted."
The US government said Shakeri is believed to be in Tehran, though he has spoken five times to the FBI over the phone.
Afghan national Shakeri came to the US as a child and served 14 years for a robbery before he was deported in 2008.
Rivera was convicted of second-degree murder in 1994 and met Shakeri when they were both doing time at Fishkill prison.
News of the plot came hours after sources in Trump’s transition team said the President-elect would apply maximum pressure on Iran.
Trump’s staff previously said the FBI had foiled the plot but stressed it was unrelated to two assassination attempts during the campaign.
Trump’s staff requested unprecedented levels of extra security including a ballistic glass shield at rallies in swing states.
In late September, Trump wrote on his Truth Social platform: “Big threats on my life by Iran. Moves were already made by Iran that didn’t work out, but they will try again. Not a good situation for anyone.
“I am surrounded by more men, guns, and weapons than I have ever seen before….
“An attack on a former President is a Death Wish for the attacker!”