The satellite rotated at 15 rpm, imaging by reconstructing the Fourier components from the time modulation of the solar x-ray flux through a set of 9 grids each 9 cm in diameter. It was expected to make images with a resolution of 2 arcseconds at 40 keV energies and 36 arcseconds at 1 MeV energies. The launch delays meant that HESSI missed some of the best flares at solar max. References: 2, 552, 554.

In the course of five spacewalks, the crew installed new equipment on HST. This was the first flight of Columbia since the launch of Chandra in 1999 following refurbishment. In the first two spacewalks, two new solar arrays were installed, and the two old arrays stowed on the RAC carrier. The RWA-1R reaction wheel assembly on the MULE carrier replaced the faltering RWA-1 in the telescope. The third spacewalk was the most difficult, as HST was entirely powered down while astronauts replaced its power controller unit, not designed for on-orbit replacement. On the fourth spacewalk the astronauts removed the European FOC camera, aboard HST since launch in 1990, and replaced it with the new ACS (Advanced Camera for Surveys). They also installed the CASH wire harness, part of the aft shroud cooling system. On the final spacewalk, the astronauts installed the NCS (NICMOS cooling system) cryocooler in the aft shround and the associated NCS radiator on the telescope's exterior. The NICMOS infrared camera had been idle since its original thermal control system failed. With the removal of FOC, the COSTAR device (which deployed contact lenses for the original instruments) became obsolete, since the newer instruments made the corrections to the incorrect HST mirror internally. Cargo manifest:

• Middeck:4 EMU spacesuits - 480 kg
• Bay 4: RAC (Rigid Array Carrier) - 2393 kg. The RAC carried the two folded SA-III rigid solar arrays which replaced the SA-II roll-up arrays. It calso carried the DBA2 diode box assembly which controlled the arrays, and a wire harness and containers associated with the NICMOS cooling system.
• Bay 7-8: SAC (Second Axial Carrier) - 2517 kg. The SAC was a specially designed pallet that flew on the first two Hubble SM flights, STS-61 and STS-82. On this flight it carried the ACS camera up (and the FOS camera down) as well as the NCS cryocooler, the PCU-R power controller, the CASH wire harness, and the thermal covers used in the PCU replacement.
• Bay 11: FSS (Flight Support System) - 2111 kg. The FSS first flew on STS 41-C (the Solar Max Repair) and was reused for each of the HST SM flights. It carried the BAPS Berthing and Positioning System, which was the docking ring for HST. Stowed on the FSS were a support post for BAPS and a cover for the HST low gain antenna.
• Bay 12: MULE (Multi-Use Lightweight Equipment Carrier) - 1409 kg. The MULE carried the NCS radiator, the NCS electronics support module, and the RWA-1R reaction wheel unit. MULE first flew on STS-48 carrying the UARS satellite, and then on STS-95 carrying the HOST payload which tested out the NCS.
• Sill: RMS arm No 201 - 410 kg