The mission was remanifested as STS-35 during the long stand-down after the accident with the addition of the Broad Band X-ray Telescope (BBXRT-01), and the original ASTRO-1 payload was brought out of storage and recertified for flight.

NASA managers concluded that Columbia had experienced separate hydrogen leaks from the beginning: one of the umbilical assembly (now replaced) and one or more which had resurfaced in the aft compartment.

The STS-35 mission was put on hold until problem resolved by a special tiger team assigned by the Space Shuttle director.

Another mini-tanking test was conducted on October 30, 1990, using special sensors and video cameras and employing a see-through Plexiglas aft compartment door.

A scheduled launch date of November 30, 1990, was moved by several days due to concerns that observations of astronomical targets would be adversely affected.

Liftoff on December 2, 1990, was delayed by 21 minutes to allow the U.S. Air Force time to observe low-level clouds that might impede the tracking of the Shuttle's ascent.

Liftoff finally occurred on December 2, 1990, 1:49:01 a.m. EST, the ninth night launch in shuttle history and the second for Columbia.

The primary payload of mission STS-35 was ASTRO-1, the fifth flight of the Spacelab system and the second with the Igloo and two pallets train configuration.

[4] The Broad-Band X-Ray Telescope (BBXRT) and its Two-Axis Pointing System (TAPS) rounded out the instrument complement in the aft payload bay.

The payload specialist set up each instrument for the upcoming observation, identified the celestial target on the guide television, and provided the necessary pointing corrections for placing the object precisely in the telescope's field of view.

[6] Issues with the pointing precision of the IPS and the sequential overheating failures of both data display units (used for pointing telescopes and operating experiments) during the mission impacted crew-aiming procedures and forced ground teams at Marshall Space Flight Center (MSFC) to aim the telescopes with fine-tuning by the flight crew.

Despite the pointing problems, the full suite of telescopes obtained 231 observations of 130 celestial objects over a combined span of 143 hours.

Problems also affected one RCC thruster and an onboard text and graphics teleprinter used for receiving flight plan updates.

[8] A ground-based experiment to calibrate electro-optical sensors at Air Force Maui Optical Site (AMOS) in Hawaii was also conducted during the mission.

The Space Classroom Program, Assignment: The Stars project was carried out to spark student interest in science, mathematics and technology.

Mission Specialist Hoffman conducted the first classroom lesson taught from space on December 7, 1990, in support of this objective, covering material on the electromagnetic spectrum and the ASTRO-1 observatory.

The mission was cut short by one day due to impending bad weather at the primary landing site, Edwards Air Force Base, California.