Hawley, the resident astronomer of the STS-93 crew, will continue his work with the Southwest Ultraviolet Imaging System, or SWUIS instrument, to collect imagery of targets associated with Mercury, Venus, Jupiter and the Moon. Although small, the sensitive SWUIS system has unique attributes that make it a valuable complement to more expensive space observatories such as the Hubble Space Telescope. Among these attributes are SWUIS's unusually wide field of view (up to 30 times Hubble's) and its ability to observe objects much closer to the Sun than most space observatories. This latter capability allows SWUIS to explore the inner solar system -- something few other instruments can do.
Collins and Ashby will be responsible for maneuvering Columbia in support of various experiments including observations made with the SWUIS telescope or the Midcourse Space Experiment (MSX), which uses sophisticated sensors to collect ultraviolet, infrared, and visible light data of firings of the shuttle's orbital maneuvering system engines or primary reaction control system jets.
Collins also will conduct a conversation with students at the Harbor View Elementary School in Corona Del Mar, California using the Shuttle Amateur Radio Experiment (SAREX) system. She also will check experiments associated with the Cell Culture Module (CCM) and the Biological Research In Canister (BRIC) payloads.
At 4:36 a.m. CDT on Sunday, Collins and Coleman will conduct an interview with CBS Radio Network. Coleman also will be interviewed by Donna Shirley, former mission manager for the Mars Pathfinder Project, in conjunction with the National Endowment for the Arts' Mars Millenium Project.
Coleman will work with the Plant Growth Investigations in Micro-Gravity (PGIM) and the Lightweight Flexible Solar Array Hinge (LFSAH) experiments, and document on-orbit operations with High Definition Television (HDTV) equipment.
Ashby will tend to various orbiter systems and check the Space Tissue Loss (STL) experiment. STL is a payload designed to validate models of bone and muscle loss induced by the weightless environment of space.
Tognini will use the SAREX system to conduct a ham radio conversation with fellow French astronaut Jean-Pierre Haignere who is currently flying aboard the Russian Mir Space Station. That communication opportunity is planned for early Sunday morning at 12:33 a.m. CDT. He'll also help check the BRIC and LFSAH experiments, and work with experiments in the Commercial Generic Bio-Processing Apparatus (CGBA).
While the STS-93 crew presses on with the remainder of its flight, the Chandra X-Ray Observatory team at the Operations Control Center in Cambridge, Mass., is preparing for the first burn of Chandra's Integral Propulsion System. The firing is scheduled for about 8:11 p.m. CDT on Saturday, July 24. Two of Chandra's four Liquid Apogee Engines will burn for approximately five minutes. Tonight's burn will be the first of four apogee burns that will result in an increase to Chandra's perigee. Later in the mission, there will be one perigee burn to increase the spacecraft's apogee. There are four engines, two primary and two redundant. Each engine has 105-pounds of thrust and uses hydrazine as fuel with nitrogen tetroxide as the oxidizer.
Following the first Integral Propulsion System burn, the new perigee is expected to be 750 miles (1,200 kilometers) and the new apogee is expected to be 45,014 miles (72,023 kilometers). Chandra's new orbit duration will be 24 hours, 38 minutes, slightly longer than its current orbit of 24 hours, 17 minutes.
Columbia is orbiting at an altitude of 158 x 148 nautical miles circling the Earth once every 90 minutes.