STS-77 Mission Control Center 
Status Report #15

Sunday, May 26, 1996 -- 8 a.m. CDT

Endeavour's crew spent the first half of its eighth day on orbit
working with experiments and helping payload controllers troubleshoot
unexpected readings by equipment designed to acquire data on the
PAMS-STU satellite's ability to stabilize itself.

Commander John Casper and Pilot Curt Brown watched over orbiter
systems and helped Bursch and payload controllers on the ground
investigate potential causes of the failure of the Attitude
Measurement System to effectively lock on to reflective targets
mounted on the PAMS-STU satellite. Even though video of the satellite
and information from the shuttle's radar system showed the
satellite in a stable attitude using aerodynamic stabilization rather
than propellant for control, the AMS continued to lock on to an
unknown target that may be an undetermined structure in the payload
bay.

Troubleshooting is continuing and experts on the ground are discussing
what course of action to take leading up to tomorrow's third and
final planned rendezvous with the small satellite.  Scientists asked
to postpone the final encounter by 24 hours to allow time to evaluate
the laser-based measuring system designed to record data accurate to
one-tenth of one degree.

The astronauts took time out from their schedule to discuss the
progress of the mission with reporters. Casper said the flight has
been highly successful so far, having accomplished all of the goals
set out before launch.

Overnight, Mission Specialists Dan Bursch and Andy Thomas described
protein crystal growth and plant growth experiments being conducted
throughout the flight in the Spacehab module.  Meanwhile, Mario Runco
tested soft drink samples in the Fluids Generic Bioprocessing
Apparatus and Marc Garneau checked sample growth in the Commercial
Float Zone Furnace.

The crew will go to sleep at 1:30 p.m. today and will wake up at 9:30
tonight.

The JSC Newsroom is open around the clock during the STS-77 mission.