Revised June 1995

KSC Release No. 32-95

STS-70
DISCOVERY/TDRS-G

	Assuring the continued full capability of NASA’s 
orbiting communications network is the primary purpose of 
Space Shuttle Mission STS-70. The Tracking and Data 
Relay Satellite-G (TDRS-G) to be deployed during the 
mission will become an on-orbit spare in the advanced 
TDRS System (TDRSS).
	In addition to TDRS-G, the Shuttle Discovery also 
will carry a crew of five and a number of smaller payloads 
on its 21st spaceflight. Liftoff will occur from Launch Pad 
39B, at a 28.45-degree inclination to the equator into a 
184-statute mile (296-kilometer) orbit. Mission duration 
currently is set for eight days, but may change to five due 
to scheduling requirements. If Discovery lifts off when 
planned, it will become the 100th U.S. human spaceflight. 
	Terence "Tom" Henricks (Col., USAF) is the 
mission commander. He served as pilot on his first two 
Shuttle flights, STS-44 in 1991 and STS-55 in 1993. Kevin 
R. Kregel, the pilot, will be taking his first trip into space.  
He is a former Air Force pilot.
	Three mission specialists are assigned to STS-
70. Nancy Jane Currie (formerly Sherlock) (Maj., USA) 
has flown in space once before, on STS-57 in 1993. Also 
embarking on a second space voyage is Donald A. 
Thomas, who holds a Ph.D. in materials science. His first 
flight was STS-65 in 1994. Space rookie Mary Ellen Weber 
earned her Ph.D. in physical chemistry before joining the 
astronaut corps.
 	STS-70 will mark the maiden flight of the new 
Block I orbiter main engine. Engine number 2036 features 
the new high-pressure liquid oxygen turbopump, a two-
duct powerhead, baffleless main injector, single-coil heat 
exchanger and start sequence modifications. The 
modifications are designed to improve both engine 
performance and safety. The Block I engine will fly in the 
number one position on Discovery. The other two engines 
are of the existing Phase II design.

TDRS-G

	TDRS spacecraft are among the largest, most 
advanced communications satellites yet built. Each TDRS 
is a three-axis stabilized satellite weighing about 5,000 
pounds (2,268 kilograms) and measuring 57 feet (17.4 
meters) across the fully deployed solar panels. At its 
highest transmission rate, a TDRS can transfer in a single 
second the entire contents of a 20-volume encyclopedia. 
	The TDRS network orbits geosynchronously at
22,300 statute miles (35,888 kilometers) and looks down 
on an orbiting Shuttle or spacecraft. This means that for 
most of their orbits around the Earth, these spacecraft will 
remain in sight of one or more TDRS satellites. The full 
TDRS constellation enables user spacecraft to 
communicate with Earth for about 85 to 100 percent of the 
orbit, depending on their altitude; prior to the deployment 
of the TDRSS, spacecraft could communicate with Earth 
only when they were in view of a ground tracking station, 
typically less than 15 percent of each orbit.
	The TDRS satellites serve as relays, passing data 
between spacecraft and a ground terminal facility at White 
Sands, N.M. Because the satellites must be located within 
view of White Sands, there are brief periods at lower 
altitudes when user spacecraft over the Indian Ocean are 
out of sight of the TDRS relay, typically about six to 12 
minutes during each 90-minute orbit . This area, stretching 
slightly less than 200 miles (322 kilometers) over the 
Earth's surface, is called the Zone of Exclusion.
	The TDRSS is currently being rearranged and 
will, in the near term, include two fully operational 
spacecraft occupying the TDRS East and West slots, one 
on-orbit spare that is fully functional, a nearly depleted 
TDRS which has exceeded its planned lifetime, and a 
partially operational TDRS devoted to supporting the 
Compton Gamma Ray Observatory (GRO) by covering 
the Zone of Exclusion via a station in Australia.
	In addition to the Space Shuttle and GRO, users 
of the TDRS system include the Hubble Space Telescope, 
UARS (Upper Atmosphere Research Satellite), TOPEX 
(Topographical tracking stations has reduced NASA 
telecommunications Ocean Explorer) and the Extreme 
Ultraviolet Explorer spacecraft. Relying on the TDRSS 
rather than on ground costs by an estimated 60 percent.
	The TDRS spacecraft with its attached upper 
stage, a 32,500-pound (14,742-kilogram) Inertial Upper 
Stage (IUS) rocket booster, is deployed from the orbiter 
payload bay about six hours into the mission. The IUS will 
ignite to propel the TDRS-G to geostationary orbit. After 
checkout at an intermediate location, TDRS-G will be 
moved to a permanent location to serve as an on-orbit 
spare. It will be redesignated as TDRS-7 once on-orbit.
       The current effort of rearranging the on-orbit 
constellation involves moving TDRS-3 into the 275-
degrees west longitude slot to replace TDRS-1. NASA is 
pulling -- for the time being -- the oldest TDRS from active 
service.TDRS-1 has operated well beyond a nominal life 
expectancy of 10 years; its future is still being evaluated. 
TDRS-3 will continue to provide the same support as has 
been provided by TDRS-1 to GRO via a ground tracking 
station in Tidbinbilla, Australia. Data relayed to the 
Tidbinbilla station is uplinked to a domestic 
communications satellite and then relayed to the White 
Sands ground tracking facility.
	Its location above the Indian Ocean also will 
allow TDRS-3 to perform an additional service during the 
upcoming Shuttle-Mir docking missions: assuring 
continuous unbroken communications with the Shuttle by 
eliminating the Zone of Exclusion for these flights.
	TDRS-G is the last in the current generation of 
TDRS satellites which includes TDRS-1 through 7. All are 
built by TRW, Redondo Beach, Calif.

Middeck Payloads

	A number of smaller payloads will be flying in the 
middeck of Discovery. The Physiological and Anatomical 
Rodent Experiment/National Institutes of Health-Rodents 
(PARE/NIH-R) is a series of experiments designed to 
determine whether exposure to microgravity results in 
physiological or anatomical changes in rodents. The 
Bioreactor Demonstration System (BDS) is a continuing 
examination of the effects of microgravity on cell growth. 
The Commercial Protein Crystal Growth-III (CPCG-III) 
seeks to grow and retrieve highly structured protein 
crystals of sufficient size to allow analysis of the molecular 
structures of various proteins and to obtain information on 
the dynamics of protein crystallization. The Space Tissue 
Loss/National Institutes of Health-B (STL-B) is designed to 
validate models of muscle, bone and biochemical and 
functional loss induced by the stress of microgravity.
	The Biological Research in Canisters-III (BRIC-
III) experiment will investigate the effects of spaceflight on 
plant specimens. The Visual Function Tester-4 (VFT-4) is 
designed to measure near and far points of clear vision, as 
well as the ability to change focus within the range of clear 
vision. VFT-4 will provide data to evaluate on-orbit 
changes in vision over a period of several days.
	The Handheld, Earth-Oriented, Real-Time, 
Cooperative, User-Friendly, Location Targeting and 
Environmental System (HERCULES) is designed to 
provide the capability to locate ground sites within one 
mile. The objective of Microcapsules in Space-B (MIS-B) is 
to demonstrate the feasibility of producing pharmaceutical 
microcapsules in a microgravity environment. The Window 
Experiment (WINDEX) will obtain spectrally isolated 
images of Shuttle surface glow, thruster plumes, aurora 
and airflow. The Radiation Monitoring Experiment (RME-
III) investigation will record both rate and total dosage of 
ionizing radiation. The Military Applications of Ship Tracks 
(MAST) investigation is studying the characteristics of  the 
tracks left by ships in the ocean.
	In the Shuttle Amateur Radio Experiment-II 
(SAREX-II), crew members communicate with ground-
based amateur radio operators and students around the 
world. Two investigations, the Air Force Maui Optical Site 
Calibration Test (AMOS) and Midcourse Space 
Experiment (MSX), require no onboard hardware. In 
AMOS, the orbiter flies over the Maui facility and helps to 
support calibration of its infrared and optical sensors. In 
MSX, orbiter thruster firings are used as a calibration and 
evaluation target for sensors on the MSX military satellite.

KSC Processing

	TDRS-G arrived at KSC on April 7 to begin final 
preparations for flight. After being mated to the IUS on 
April 12, the TDRS-G/IUS assembly was taken to the 
launch pad to await installation in Discovery’s payload 
bay. Discovery flew once earlier this year, becoming the 
first orbiter in the fleet to notch 20 spaceflights.