The mission restored the spaceborne observatory's vision (marred by spherical aberration in its mirror) with the installation of a new main camera and a corrective optics package (COSTAR).

STS-61 lasted almost 11 days, and crew members made five spacewalks (extravehicular activities (EVAs)), an all-time record; even the re-positioning of Intelsat VI on STS-49 in May 1992 required only four.

During the flight, mission specialist Jeffrey A. Hoffman also spun a dreidel for the holiday of Hanukkah to a live audience watching via satellite.

The internal HST payload package was not affected because it was tightly sealed, and the contamination appeared to have been caused by sandblasting grit from recent Pad A modifications.

The first launch attempt on December 1, 1993, was scrubbed due to weather constraint violations at the Shuttle Landing Facility.

[2]: 2  Just before the scrub the range was also in a no-go situation due to an 240 m (790 ft) long ship in the restricted sea zone.

Endeavour performed a series of burns that allowed the shuttle to close in on the Hubble Space Telescope at a rate of 110 km (68 mi) per 95-minute orbit.

HST was sighted by astronaut Jeffrey A. Hoffman using binoculars, whereupon he noted that the right-hand solar array was bent at a 90° angle.

These 12 m (39 ft) solar arrays, provided by the European Space Agency (ESA), were scheduled to be replaced during the second spacewalk because they wobbled 16 times a day (as the telescope heated up and cooled off while passing from the nighttime side of the Earth to the daytime side and vice versa), thus disturbing Hubble's ability to maintain precise pointing.

[4] The multi-axis RCS terminal initiation (TI) burn, which placed Endeavour on an intercept course with HST and set up commander Dick Covey's manual control of the final stages of the rendezvous, occurred at 05:35 UTC.

[5] After capture, additional visual inspections were performed using the camera mounted on the 15 m (49 ft)-long shuttle remote manipulator arm (Canadarm).

Story Musgrave and Jeffrey A. Hoffman started the first EVA about an hour earlier than scheduled by stepping into the cargo bay at 03:46 UTC.

Hoffman then installed a foot restraint platform onto the end of the shuttle's remote manipulator arm (Canadarm), which he then snapped into his feet.

Engineers who evaluated the situation speculated that when the doors were unlatched and opened, a temperature change might have caused them to expand or contract enough to keep the bolts from being reset.

With the efforts of determined astronauts in Endeavour's payload bay and persistent engineers on the ground, all four bolts finally latched and locked after the two spacewalkers worked simultaneously at the top and bottom of the doors.

Astronauts Thomas D. Akers and Kathryn C. Thornton replaced HST's solar arrays during the second planned EVA (Thornton had red dashed stripes on her spacesuit while Tom Akers had diagonal red dashed stripes, which helped flight controllers tell the two spacewalkers apart).

The crew decided to use a technique of relaying all commands for Thornton via Akers instead of switching to the backup comm channel.

Akers started the EVA by installing a foot restraint on the Canadarm for Thornton and proceeded to begin disconnecting three electrical connectors and a clamp assembly on the solar array.

The jettison during daylight allowed the astronauts and flight controllers to accurately track its position and relative velocity.

After the 6.5 hours EVA, successful functional tests were performed by the Space Telescope Operations Control Center (STOCC) on four of HST's six gyros.

Hoffman attached the support handle to the WF/PC and, with assistance by Claude Nicollier on the arm and a free floating Story Musgrave, removed the WF/PC during the night pass starting at 04:41 UTC.

The new Wide Field and Planetary Camera 2 had a higher rating than the previous model, especially in the ultraviolet range, and included its own spherical aberration correction system.

The doors were scheduled to be opened during a night pass to minimize thermal changes and reduce the possibility of out-gassing of components that could contaminate the optics.

HSP was then parked on the side of the payload bay while COSTAR was removed from stowage and successfully installed in the HST by about 05:35 UTC.

After much analysis by a team at the GSFC, it was determined that the dump failure was due to noise on the communications link between the spacecraft and the ground.

Endeavour was placed in free drift to disable any RCS firings that could disrupt the solar arrays and the PDM motors were engaged at 03:48 UTC.

After the SADE was replaced the crew fitted an electrical connection to the Goddard High Resolution Spectrograph at 08:30 UTC and it passed its functionality test.

Flight Day 9 began on December 9, 1993, but concerns about one of HST's four onboard Data Interface Units (DIUs) delayed release.

Each of the 16 kg (35 lb) DIUs transfer data between the HST's main computer, solar arrays and other critical systems.

Commander Dick Covey and pilot Kenneth D. Bowersox fired Endeavour's small maneuvering jets and moved the shuttle slowly away from HST.