As a teenager, he came to the United States, where he earned degrees in aerospace engineering, became a US citizen and cofounded a pioneering satellite telecommunications company that at one point was worth up to $500 million. He seemed on the verge of the kind of success that immigrants dream of achieving.

Today, those dreams are burning up like a spacecraft in steep reentry.

Modanlo’s company is bankrupt, his US and Iranian passports have been confiscated and a federal judge has ordered him to wear an electronic monitoring bracelet while he sleeps.

A federal grand jury indicted the Maryland resident last year on charges he secretly brokered the launch from Russia of the first Iranian-owned satellite in 2005, in violation of the US sanctions against Iran. If convicted on all counts, he could be sentenced to 65 years in prison and ordered to pay $10 million. Five Iranian nationals were also indicted, but none is in custody.

Iran went on to launch its first satellite aboard an Iranian-built rocket in 2009 and its second earlier this month. Jonathan McDowell of the Harvard-Smithsonian Center for Astrophysics said the June 15 launch of the tiny Rashad-1 satellite, a 34-pound orbiter, shows the country is well on its way to mastering the multi-stage rocket technology that would be needed for long-range nuclear missiles.

McDowell called it an impressive record for a country in the early stages of its space program.

“They might have a couple of more failures in the next couple of launches,” he said. “But after that, they will basically have the capability to know what they’re doing.” Modanlo, 50, denies that he violated US sanctions and is free on $250,000 bond.

He refused through his lawyers to be interviewed, and officials from the Justice Department and US Immigration and Customs Enforcement likewise refused to discuss the case. But experts, court documents and other public records describe how his ambitions might have led him into trouble. The trial is expected to begin in October 2012.

The 2005 launch from Russia of the Sina-1 satellite came one day after newly elected Iranian President Mahmoud Ahmadinejad said Israel must be “wiped off the map.” To many, the launch seemed to back up this threat.

David Albright of the Institute for Science and International Security, an expert on nuclear proliferation, said Iran is focused on the military applications of space science. “One of the goals of the program, and it appears to be an ongoing program, is to develop a missile that can carry a nuclear warhead if Iran decides to build one,” he said.

The Justice Department said Modanlo’s case is just one of more than 150 filed by prosecutors in the past four years against arms traders and middlemen suspected of helping Tehran illegally acquire US technology. Defendants have been accused of using shell companies, offshore bank accounts and faked end-user certificates to supply Tehran with everything from US-made component parts for missile guidance systems to the ultra-high-strength steel needed to build centrifuges that enrich uranium.

Yet Modanlo’s case stands out. Unlike most of those prosecuted under the act, he isn’t charged with shipping US technology to Iran. Instead, he is suspected of using his business contacts and aerospace engineering experience to help launch Iran’s space program.

Modanlo said he came to the US from the Iranian city of Sari on the Caspian Sea coast in 1979 — the year of the Islamic revolution, according to interviews with The Washington Post and other publications in the 1990s. After earning degrees in engineering and aeronautics from George Washington University, he worked on projects for the Defense Department and NASA.

Modanlo and business partner Michael Ahan in 1992 founded Final Analysis Inc., based in offices near NASA’s Goddard Space Flight Center. They planned to loft a network of up to 32 small, low-earth orbiting telecommunications satellites that were designed to provide low-cost messaging and cargo tracking services.

“It was a good idea, and he (Modanlo) was one of the early guys thinking about it,” said researcher David Boyle of Texas A &M University, whose lab developed communications gear for Final Analysis.

Modanlo’s plan was to save millions by launching half-a-dozen communications satellites at a time using Soviet ICBMs, designed to carry multiple nuclear warheads aimed at the US He and Ahan signed a deal with a top former Soviet missile scientist, Alexander I. Ilyin of Gloria Polyot, or “Glory Flight” in English. The private company employed scientists and technicians working at a missile factory in the Siberian town of Omsk.