yee@trident.arc.nasa.gov (Peter E. Yee) (05/29/90)
Patricia Phillips May 27, 1990
407-867-2468
KSC Release No. 95-90
STS-35 PAYLOAD TEAM COMPLETES MAJOR PRELAUNCH MILESTONES
As the Kennedy Space Center launch team continues to count
down toward the launch of Columbia at 12:38 a.m. May 30, members
of the payload processing team are closing out the final tasks
for the Astro-1 payload.
Today, the payloads team completed the final servicing of
the Broad Band X-Ray Telescope with solidified argon. Since its
arrival at KSC in late l989, the BBXRT has required servicing
with argon at regular intervals -- usually every 10 days -- in
order to keep the sensitive instrument cooled.
This final BBXRT coolant servicing was planned to protect
both the planned mission flight time for BBXRT, and also to
provide the greatest amount of flexibility in the launch environ-
ment. Based on current mission planning, the payloads team ap-
proach will provide up to 6 launch opportunity days.
The solidified argon will maintain BBXRT for about 16 days.
Of that time, prelaunch operations after the conclusion of ser-
vicing will deplete about 2.5 days of argon capability, leaving
3.5 days for launch attempts. Since the primary science objec-
tives for BBXRT could be accomplished in 8 flight days of the
10-day mission, the payloads community agreed to add an addi-
tional 2 days for launch tries. This boosted the total launch at-
tempt opportunities to about 6 days.
About 97 pounds of argon are used in each of the two dewars
for BBXRT, providing a toal of 194 pounds. In addition, about 60
pounds of liquid helium is circulated around the dewars to
enhance and retain the chilling.
In other preflight activities, installation of the
Ultraviolet Imaging Telescope (UIT) film pack was completed about
2 a.m. yesterday morning. The film will be removed up to 4 days
after landing at Edwards Air Force Base, California.
During the launch countdown, BBXRT's temperature will be
monitored, with checks ranging from every 30 minutes to every
four hours. Other payload preflight activities include the final
payload changeout room (PCR) walkdown, the installation of addi-
tional argon outgassing valves on the BBXRT, verification of the
operation of the Vacuum Maintenance System (VMS) on the BBXRT,
briefly powering up the BBXRT for checks, and deactivating the
Hopkins Ultraviolet Telescope (HUT) vacuum ion pump when the T-0
umbilical power is removed at T-9 minutes. BBXRT T-0 powered ac-
tivities will conclude at the T-23 minute point.
After Columbia's payload bay doors close, the payloads team
will be looking forward to the conclusion of a processing flow
that originally began in l985. When remanifested for this year,
BBXRT was added to ASTRO-1, and the Wide Field Planetary Camera
was removed. Astro-1 marks the return to flight of primary
horizontal payloads. The last one processed and flown was Mission
61-A, the German Spacelab (D-1) mission in October/November,
l985.
Astro-1 uses two Spacelab pallets, an instrument pointing
system (IPS) and an "igloo" as part of its support hardware.
Spacelab equipment is a set of manned and umanned modular com-
ponents developed by the European Space Agency (ESA). For each
payload using Spacelab components, specific standardized parts
are combined to support mission requirements -- in essence, a
high-tech "mix and match." On this flight, only the IPS has flown
before, on the Spacelab 2 mission in July/August, l985 (51-F).
BBXRT is carried on its own unique two-axis pointing system
(TAPS).
The challenges of preparing a payload to final testing, then
deintegrating it, and later reintegrating it with different
equipment, has demonstrated the versatility of the KSC payloads
team, according to KSC NASA payload processing manager Glenn
Snyder.
"They've shown patience, flexibility, and dedication. After
all this time, we're ready to go fly! The team is excited to see
all their work come together for launch," he added.