Resumption of the countdown after the T−9-minute hold was delayed about 4 minutes 45 seconds because of two possible weather-condition violations of the launch commit criteria (LCC).

CGRO was launched on a two-year mission to search for the high-energy celestial gamma ray emissions, which cannot penetrate Earth's atmosphere.

The first U.S. extravehicular activity (EVA) or spacewalk since 1985 was performed by Mission Specialists Ross and Apt after six failed attempts to deploy the satellite's high-gain antenna.

During the second EVA, a stainless steel palm restraint bar punctured the pressure bladder of Apt's right glove.

[3] Secondary payloads included Crew and Equipment Translation Aid (CETA), which involved scheduled six-hour spacewalk by astronauts Ross and Apt (see above); Ascent Particle Monitor (APM); Shuttle Amateur Radio Experiment (SAREX II); Protein Crystal Growth (PCG); Bioserve/Instrumentation Technology Associates Materials Dispersion Apparatus (BIMDA); Radiation Monitoring Equipment (RME Ill); and Air Force Maui Optical Site (AMOS) experiment.

It was arguably the first time that the astronauts received fast scan amateur television video from the ham radio club station (W5RRR) at Johnson Space Center (JSC).

The landing was originally scheduled for April 10, 1991, but was delayed one day by weather conditions at Edwards and Kennedy Space Center (KSC).

An incorrect call on winds aloft caused Atlantis to land 623 feet (190 metres) short of the lakebed runway's threshold marking.

The stars also represented the Amateur Radio term "73" or "Best regards", consistent with the fact that the entire crew had become licensed and operated the SAREX-II experiment while on orbit.