Conference 7.286::space

Subject: Launch Aborted
Posted: Sat Jul 13 22:40:18 1985
Organization: Bell Labs, Murray Hill
 
The Challenger's launch attempt was aborted today, just
three seconds before SRB ignition.  In a near replay of
the abort last summer, a valve that regulates the flow
of hydrogen into the Number 2 Engine did not respond to
its primary control circuit.  A backup circuit sent the
proper command 40 milliseconds after the failure was
detected, but by that time, the ground sequence computer
decided to abort the launch -- NASA rules forbid a launch
unless all systems, including redundancies, are functioning,
so that backups will be available once in flight.  At the
time of the abort, two engines were at full power, while
the Number 2 Engine was near it.  A water spray system,
installed after last summer's abort and proceeding fire,
activated, but there was no fire.  NASA said the launch
will be delayed at least 7 to 10 days while an assessment
of the problem is made.


Subject: Actuator Thought to be Problem
Posted: Sun Jul 14 22:13:20 1985
Organization: Bell Labs, Murray Hill
 
NASA said today that technicians believed yesterday's abort
to be due to a faulty actuator on a hydrogen cutoff valve.
The actuator will be removed Sunday for extensive testing,
and NASA officials will meet Monday to decide how to proceed 
-- whether to set another launch date or move the Challenger
off the pad and delay its mission indefinitely.  Timing becomes
critical now.  Columbia is scheduled to arrive at the Cape
on Sunday, marking the first time all four shuttle have
been at the space centre.  Atlantis is due to be moved into
the VAB this week for mating with SRB's and ET and then
moved to the launch pad for a flight readiness test firing
(lasting 20 seconds) on 30 July.  If Challenger's launch
is set for later this month, that firing will be delayed,
thereby postponing Atlantis' maiden mission, now set for
mid-September.  Discovery is due to launch on 24 August;
its mission will be to deploy three communications satellites
and attempt to rescue to the stranded Syncom satellite.
The launch window for that mission is only four days
wide.  Columbia's next launch, its first after its
recently completed overhaul, is set for December.

Can any of you space buffs tell me what a "launch window" is?  It is
easy to assume that if you propel any object into space at or above
the critical speed that it will reach orbit!

Thanks
Mark

A launch window is the period of time during which a launch should take place
in order to reach the desired destination.  Since the rest of the universe
is not standing still as the Earth rotates and revolves about the sun, our
position relative to astronomical objects changes.  It may not be possible
to carry enough fuel to get to some planet, but if you time it right, you
could use the slingshot effect from the gravity of a planet along the way.
There is only a certain time period (launch window) in which the correct
configuration of planets is available.  There are similar examples for getting
to a satellite, the moon, or whatever else you need to fly to.

---Phil

Thanks very much for the information.

I can understand "launch window" in the context of a flight to the 
moon (say), but I'm not sure I understand how it applies to earth
orbit? It seems as though there is nothing to use as a slingshot.
Does it have anything to do with the moon pulling the shuttle off
the desired orbit?


Thanks
Mark

Subject: Launch Rescheduled
Posted: Mon Jul 15 14:59:37 1985
Organization: Bell Labs, Murray Hill
 
Xref: tektronix net.columbia:01368 
 
Workers today replaced the faulty valve in the Challenger's
Number 2 Engine and rescheduled its launch for 1500 EDT, 29
July.  That could be changed by two days either way.  The
change in schedule maintains a 24 August launch date for
the Discovery but pushes a test firing of Atlantis' main engines
from 30 July to 12 September.  Atlantis' maiden launch,
originally scheduled for 19 September now slips to late
September or early October.  Challenger's 30 October launch
was moved to early November, but the 27 November Atlantis
and 20 December Columbia flights are preserved.  If the problem
with Challenger turns out to be more severe than the one
suspected, its mission may be delayed until next year; as
a purely scientific flight, it has lower priority than
commericial and DoD flights.
 
A second launch pad, 39B, will become available at KSC in
January, helping NASA to meet its tight schedule.  Also next
year will be the first launch from VAFB, scheduled for March;
the Discovery is expected to be assigned there permanently.

Subject: Challenger to Launch Monday
Posted: Tue Jul 23 04:34:17 1985
Organization: Bell Labs, Murray Hill
Xref: tektronix net.columbia:01380 
 
NASA yesterday rescheduled the aborted launch of the
Challenger for 1523 EDT, 29 July.  Landing will be
seven days later at EAFB.  The valve actuator and control
system from the Number 2 Engine, suspected to the be
cause of the abort, were replaced, and all engines
tested thoroughly.  Although a computer controlling
an array of experiments in the cargo bay failed, NASA
said a backup could do the job -- the main computer is
inaccessible on the launch pad.

                          By CHARLES J. LEWIS
                        Associated Press Writer
   CAPE CANAVERAL, Fla. (AP) - Scientists kept their fingers
crossed that a failed computer wouldn't spoil 10 years of planning
and $78 million worth of experiments aboard the space shuttle
Challenger as the countdown ticked off toward Monday's 3:23 p.m.
EDT launch.
   The flight is to make up for the launch that was aborted July 12
when a computer sensed that a valve in Challenger's No. 2 engine
didn't close properly and shut down all sthree main engines just
three seconds before liftoff.
   Meteorologists kept close watch Sunday over weather conditions
at two airports in Spain and one at White Sands, N.M., where the
shuttle would land in an emergency. Clouds and poor visibility
there would prevent landings and could result in yet another launch
delay.
   The mission is so crammed with scientific experiments that
scientists aboard are scheduled to work around the clock in 12-hour
shifts during the seven-day flight, scheduled to conclude Aug. 5
with landing on the desert runway at Edwards Air Force Base, Calif.
   It will be only the third afternoon launch in 19 shuttle
flights. The time is determined by lighting requirements for some
astronomy experiments.
   The failed computer was discovered July 18 when engineers were
resetting some of the experimental equipment in Challenger's cargo
bay. They turned on power to reset a key tape recording system and
the computer, one of three in the cargo bay, turned on briefly but
then shut down.
   The failed computer was supposed to control some of the 10
scientific experiments in the cargo bay. A second computer is to
measure the results of those experiments and a third computer was
the backup for either of the other two.
   The third computer was switched to take over running the
experiments, leaving the system with no backup computer.
   The lack of a backup was an acceptable risk, John W. Thomas,
manager of spacelab operations, said Sunday. He said it was
impossible to replace the failed computer without delaying the
mission again.
   Any further delay of the research mission might knock it off the
launch schedule in favor of planned flights carrying satellites for
paying customers.
   ``If we lose the experimental computer (again), for the most
part, from a science viewpoint, it would be a lost mission,'' said
Roy Lester, manager of this Spacelab mission.
   Three experiments in the shuttle cabin don't depend on the
cargo-bay computers and could be carried out in case another
computer fails. But any repeat computer failure once in orbit would
lead to a shortened mission, possibly to four days, Lester said.
   Other NASA officials later said that testing the instrument
pointing system - a key goal of the mission - could be done with
only one cargo-bay computer working.
   The German-built system is designed to aim telescopes and radar
antennas at Halley's Comet during a shuttle mission next March.
   Sam Keller, director of NASA's science programs, said testing
the instrument pointing system was the most important part of the
science mission.
   ``Because of the Halley mission, it's vital that we get this
mission,'' Keller said. ``It's the most important objective of this
mission.''
   The delay caused by the July 12 abort will interfere with some
of the experiments, said Eugene Urban, manager of scientific
experiments on the mission. The original date was chosen because
the moon then was in its new phase, near the sun, and provided a
darker sky desired for some astronomical experiments.
   Urban said the brighter phase of the moon now will cause a 15
percent loss in the use of an infra-red telescope and similar
losses in two studies of the plasma, or electrified gas,
surrounding the Earth.
   But on the positive side, Urban said, the delay allowed
engineers to repair an experiment cooled by 26 gallons of liquid
helium. That proje8ct had been scrubbed two days before the earlier
launch date because of a leaky helium pump.
   Asked to assess the net effect of the delay, he said, ``It's a
wash.''
   Regardless of the scientific knowledge gained during the
mission, Challenger's flight on NASA mission 51-F will likely be
remembered for its contribution to the ``cola war'' between
Coca-Cola and Pepsi-Cola.
   Each soft drink company has four cans of its product aboard to
test methods of dispensing carbonated beverages in space. Each
hopes its product will be accepted by NASA.
   Scientists on the mission are geophysicist Anthony England,
astronomer Karl Henize, solar physicist Loren Acton, astrophysicist
John-David Bartoe and physician Dr. Story Musgrave. Gordon
Fullerton is the commander and Roy Bridges the pilot.
   Henize, 58, will become the oldest person to fly in space. An
astronomer, he was in the first group of scientist-astronauts named
by NASA in 1967 and has waited 18 years for his first space trip.

Re: .4 (I think)

Regarding the "launch window" of the shuttle.

Launch windows (in terms of days) for the shuttle have to do
(primarily) with the launch-a-month schedule that NASA tries so hard
to keep.  If a vehicle fails to get off the ground within a certain
timeframe, things start to bind up (there's only one assembly building
and (currently) one launch tower.

I suppose there are other windows for missing sattelites, daylight
over study areas, etc.

- dave

Subject: Countdown Starts
Posted: Sat Jul 27 20:59:37 1985
Organization: Bell Labs, Murray Hill
 
The countdown for the Challenger mission began at 0900
EDT today, and NASA reported that the ship's hydraulic
fluid had been purged of air buildup several hours ahead
of scheduled, leaving closing the aft compartment the
only job left to get back on track.  Liftoff is scheduled
for 1523 EDT Monday.


Subject: Launch Delayed by Gyro Problem
Posted: Mon Jul 29 13:54:55 1985
Organization: Bell Labs, Murray Hill
 
Just fifteen minutes before its scheduled 1523 EDT launch today,
Challenger's liftoff was again delayed, this time by a faulty
gyroscope.  The unit, one of three in one of the shuttle boosters,
failed to respond to computer commands, but the problem was
later solved, and NASA has reset the launch for 1700 EDT today.
The launch window closes at 1830 EDT.


Subject: Launch
Posted: Mon Jul 29 14:12:51 1985
 
The Challenger launched at 1700 EDT today, after an earlier
delay due to a faulty SRB gyro.


Subject: Abort to Orbit
Posted: Mon Jul 29 14:47:18 1985
 
Six minutes into its flight, Challenger lost power in its
centre main engine, and the other two engines burned 1
minute 32 seconds longer to compensate.  The crew was
instructed to abort to orbit, bypassing a possible emergency
landing in Rota, Spain.  The shuttle ended up in an
orbit ranging between 120 and 160 miles, lower than
the hoped for 240 mile circular orbit.  An OMS burn
33 minutes into flight is to circularlize the orbit.
NASA hopes that the mission can be completed to its
full seven day duration, but no decision has been
made yet.


Subject: Corrections
Posted: Mon Jul 29 15:07:45 1985
 
Two minor corrections:
 
1) The two remaining engines burned for 1:26, not 1:32
2) The elliptical shuttle orbit was 122x160 miles, instead
   of the normal 122x214 miles at that point.  The initial
   intended orbit was a circular orbit of about 140 miles,
   not 240 miles.


Subject: Failed Engine
Posted: Mon Jul 29 18:52:24 1985
 
Xref: tektronix net.columbia:01393 
 
Engine Number 1 shut down in midburn today because both
primary and backup systems reported overheating in a
high-pressure turbo fuel pump; computers shut the engine
down to avoid danger of explosion, and mission control
instructed the crew to burn the other two engines at 104%
rated thrust for the duration of their fuel.  At the same
time, some of the hydrazine fuel for the OMS was dumped
to lighten the load.  There is plenty of OMS fuel left
for reentry and most of the scientific experiments, and
NASA is confident that the mission can continue for its
full seven days.

Subject: Second Engine Almost Shut Down
Posted: Tue Jul 30 05:29:19 1985
Xref: tektronix net.columbia:01394 
 
Minutes after Engine Number 1 shut down yesterday, a temperature
sensor on the right main engine also began to show overheating.
As the backup sensor came on to verify the reading, NASA instructed
the crew to shut down the sensors and override the automatic
shutdown of that engine; fortunately, the temperature never
got high enough that that would have happened anyway.  However,
loss of a second engine at that point would have forced the
Challenger to attempt an emergency landing on the island of
Crete, and, as NASA put it, they probably would have ended
up ''in the water.''  When EN1 shut down, the ship was 33
seconds past the TAL (Trans Atlantic Abort (to Spain)) point.


Subject: Sensors Probably to Blame
Posted: Tue Jul 30 09:05:03 1985
 
NASA said today that early analysis of data from the shuttle Challenger
points to a problem with EN1's heat sensors, not the engine itself.  As
a result, the agency said that the 24 August launch of the Discovery
would go ahead as planned, with better heat sensors aboard.  The Discovery
today was moved into the VAB and will be moved to the launch pad Monday.
 
Meanwhile, the crew of the Challenger wrestled with a telescope pointing
device, testing of which is the most important goal of the mission.  The
platform will be used on a flight next spring to study Halleys' comet.
One of the telescopes on the platform also lost power, and technicians
are working on solutions to both problems.

Subject: Science Abounds on Challenger
Posted: Wed Jul 31 20:27:43 1985
 
The Challenger crew today plucked the plasma diagnostics
package from the cargo bay with the RMS and moved it around
the ship.  The device is to take readings aimed at explaining
the mysterious glowing phenomena seen around most shuttle
flights to date.  Later in the mission, the PDP will be released
and then picked up again after that.
 
Meanwhile, a $60 German-built telescope pointing system
continued to fail, despite two attempts to fix it.  The device
locked onto the sun for brief periods but then lost track
of it.  The test is important, as the palate is to be used
during the Halleys comet mission next spring.  Three of the
four telescopes on the platform are working individuallay;
the fourth lost power and is not functioning.

Subject: PDP Experiments Successful
Posted: Thu Aug  1 18:21:21 1985
Organization: Bell Labs, Murray Hill
 
Challenger astronauts today zapped the plasma diagnostic
package with an electron gun to simulate observed electron
bolt exchanges between distant stars, and ground controllers
said the experiment gathered ''fundamental data'' in helping
to explain this phenomenon.  The PDP also recorded ''fantastic
wave effects'' of the Challenger passing through the ionosphere.
 
Meanwhile, ground controllers were examining remaining fuel
supplies aboard the shuttle in the hopes that its orbit might
be raised by 8 to 10 miles.  A decision is expected by Friday.

                          By HOWARD BENEDICT
                          AP Aerospace Writer
   CAPE CANAVERAL, Fla. (AP) - Shuttle managers decided today to
extend Challenger's mission in orbit by a day, until Tuesday, to
give the astronauts more time to add to their scientific harvest
now that the ship's $60 million telescope pointer and most other
instruments are working.
   The new landing time was set for 3:47 p.m. EDT Tuesday at
Edwards Air Force Base, Calif.
   The extension was requested by ground scientists, who have
expressed delight over data being gathered by their instruments on
the sun, stars, galaxies and Earth's atmosphere.
   NASA officials made the decision after determining that
Challenger had enough fuel for the extra day, plus enough for two
contingency days beyond Tuesday. Forecasters said weather also
should be good Tuesday at Edwards.
   Challenger was slightly low on liquid hydrogen and liquid
oxygen, which are used to generate electricity, but the seven
astronauts have been conserving these consumables in case the
flight was extended, said Flight Director Al Pennington.
   The astronauts spent much of today conducting experiments and
their conversation was confined to technical exchanges with
scientists on the ground.
   They did take a few minutes to transmit to the control center
spectacular television views of a cloudless section of Earth over
which they passed. Clearly visible were the Sahara desert, the
north coast of Africa, the Mediterranean, the boot of Italy,
Greece, Turkey, the Black Sea and the Caspian Sea in the southern
part of the Soviet Union.
   ``Absolutely beautiful,'' said Mission Control.
   Mission scientists said they would like the extra day primarily
to gather data from three telescopes mounted on a $60 million
pointing system that was inoperative until Friday, when the
astronauts repaired it with a new computer program worked out on
the ground.
   During the three days the instrument was unable to point, the
astronauts used fine-aiming devices on the individual telescopes.
Each maneuver required extensive testing and calibration and cost
valuable data-gathering time.
   Astronauts Karl Henize, an astronomer, and Loren Acton, a solar
physicist, were operating the telescopes when the pointing
mechanism was fixed, and they were overjoyed.
   ``Hey, it was successful,'' Acton reported.
   ``Wow!'' exclaimed Henize. ``I'll offer another hallellujah and
hope it keeps on this time.''
   The spacemen, operating around the clock in two shifts, began an
almost non-stop survey of the sun, studying flares, sunspots and
other phenomena that might help scientists better understand how
the sun influences our solar system, including its effect on
communications and weather on Earth.
   Henize and Acton alternated with astrophysicist John-David
Bartoe and geophysicist Tony England.
   The astronaut-scientists also kept watch over a battery of
instruments measuring cosmic rays and X-rays, infrared radiation
from stars and galaxies and the gases and charged particles that
form plasma in Earth's atmosphere.
   Only one of 13 instruments was not working. That was a fourth
telescope mounted on the pointing device and designed to study
magnetic fields in the sun's atmosphere.
   Dr. Story Musgrave, a physician, continued medical experiments,
including the periodic drawing of blood from the other crew members
for study back on the ground. Flying Challenger were commander
Gordon Fullerton and pilot Roy Bridges.

Associated Press Mon 05-AUG-1985 02:39                          Space Shuttle

   Astronauts Transmit First Pictures From Restored Sun Telescope
                          By HOWARD BENEDICT
                          AP Aerospace Writer
   CAPE CANAVERAL, Fla. (AP) - Challenger's astronauts transmitted
the first pictures of the sun today from a telescope they had given
up for dead as they sailed through the final full day of their
extended scientific expedition.
   ``It's working,'' said astronaut John-David Bartoe, an
astrophysicist, early today as he viewed TV images of a sunspot
snapped by the telescope, which was measuring magnetic fields in
the solar atmosphere.
   ``Fantastic,'' replied Mission Control. ``The experimenters are
delighted.''
   ``The image looks really, really great,'' added astronaut Loren
Acton, a solar physicist. ``You can see every little granule. There
are little black spots all over the place.''
   The activation of the instrument completed the spectacular
recovery of Challenger from an unpromising beginning. The shuttle
left the Earth 17 days late because of a launch pad engine abort
and, once off the ground, an engine stalled, leaving the ship in a
lower-than-planned orbit.
   Some of the experiments also had to be repaired, but all 13 are
now up and running, including two of interest to the proposed
``Star Wars'' missile defense program.
   Astronaut Karl Henize, an astronomer, probably expressed the
feelings of the entire crew when he said today, ``This is a great
experience. I've enjoyed every minute of it since that first day.''
   The seven crewmen were scheduled to have ended their journey
today, but with shuttle and experiments working so well, NASA on
Saturday decided to keep the ship in orbit an extra day. Landing is
set for 3:47 p.m. EDT Tuesday at Edwards Air Force Base, Calif.
   The solar telescope, one of four mounted on a pointing device in
Challenger's cargo bay, had been useless, its power system
inoperative, since the beginning of the flight last Monday. After
several attempts to revive it, Mission Control anounced Sunday no
more efforts were planned.
   But experimenters decided to give it one more try Sunday
afternoon, and, inexplicably, the power came on.
   Flight director Al Pennington theorized that the power system
might have been jolted to life by two firings Sunday of
Challenger's large maneuvering rockets.
   The rockets were triggered over Australia and Massachusetts,
burning holes in the ionosphere in an experiment of interest to
researchers of President Reagan's proposed strategic defense
initiative, commonly called Star Wars.
   Ionospheric changes were recorded by the Reber Observatory in
Hobart, Tasmania, and the Millstone Hill Observatory in Westford,
Mass.
   During similar exhaust releases from ground-launched rockets,
scientists discovered that water vapor from the exhaust caused
electrons to combine with ions in the upper atmosphere, leaving
temporarily depleted plasma areas called ionospheric holes.
   Because the ionosphere reflects radio signals between distant
ground stations, researchers want to study the properties of the
holes and their effects on radio wave propagation.
   Star Wars systems would make use of lasers or particle beams
traveling in the ionospheric plasma to track and destroy attacking
missiles. The shuttle data could determine if rocket-generated
holes in the ionosphere could interrupt those beams.
   Defense Department scientists also are interested in data on the
ionosphere gathered by another shuttle experiment called the plasma
diagnostic package. The astronauts fired electron beams at the
package after it was released as a free-flying satellite.
   Other experiments were gathering information on cosmic rays,
infrared and X-ray emissions from stars and galaxies and properties
of Earth's upper atmosphere.

Associated Press Tue 06-AUG-1985 05:30                          Space Shuttle

                          By HOWARD BENEDICT
                          AP Aerospace Writer
   CAPE CANAVERAL, Fla. (AP) - Challenger's astronauts fired an
electron beam into the atmosphere as their final test today and
headed back to Earth from a research journey acclaimed by
scientists as a sensational success after a rocky start.
   They were bringing home a wealth of knowledge collected about
the solar system after the mission recovered dramatically from a
launch abort, a lost engine and failed experiments.
   Commander Gordon Fullerton and pilot Roy Bridges guided the
100-ton space plane toward an afternoon landing on a desert runway
at Edwards Air Force Base, Calif. Touchdown was set for 3:45 p.m.
EDT at the end of an eight-day, 3.3-million-mile trip acclaimed as
the most ambitious space science effort ever.
   A team of specialists waited at Edwards to inspect Challenger's
No. 1 engine in an effort to pinpoint why it shut down early during
liftoff. They suspect faulty sensors sent a false fuel pump
overheating signal but want to be sure before the next shuttle
flight, that of Discovery on Aug. 24.
   NASA is so confident bad sensors are to blame that it moved
Discovery to the launch pad today to be groomed for a mission in
which the crew will deploy three communications satellites and try
to repair a disabled one already in orbit.
   In their final experiment, the astronauts triggered an electron
generator over the Pacific Ocean, shooting a bright beam toward the
Earth from 175 miles up. An observatory on Hawaii recorded
disturbances created in the ionosphere's field of gases and
particles. It was one of several studies of the ionosphere, the
atmospheric layer that relays radio signals between distant ground
stations.
   All 13 of the experiments in the $76 million package were shut
down by 4:30 a.m., and astronauts and scientists on the ground
congratulated themselves on what Mission Control termed ``a highly
successful flight.''
   ``Happy landings,'' one control team member radioed.
   The seven-man crew was returning with miles of data tape,
thousands of photographs and 45 hours of video tape that could give
researchers a better understanding of the sun, stars, galaxies and
the gases and particles that swirl in the Earth's atmosphere.
Officials said that during the mission, ground controllers received
1.25 trillion bits of data.
   ``All the experimenters are delighted with the sensational
results of this mission, which has been 10 years in the planning,''
mission scientist Eugene Urban told reporters at Mission Control.
``Everyone has collected a tantalizing amount of data. It will be
some time before we know the scientific results. In some cases, the
experimenters have enough data to keep them busy for several
years.''
   He said the flight achieved 80 percent to 85 percent of its
science goals despite problems that included an early engine
shutdown on liftoff that left the ship in an orbit 46 miles low,
enabling the upper atmosphere to block some ultraviolet radiation
from reaching one of the telescopes; a $60 million telescope
pointing device that malfunctioned for three days before ground
specialists corrected a computer program; and the failure of one of
the four sun telescopes to turn on until two days ago.
   The astronauts nursed rocket propellant and other energy
supplies and were able to develop enough of a surplus to extend the
mission by one day.
   The flight crew included five scientists - geophysicist Tony
England, astronomer Karl Henize, solar physicist Loran Acton,
physician Story Musgrave and astrophysicist John-David Bartoe.
   ``The astronauts and the ground crews have worked together in an
amazing way,'' Urban said.
   Thus, a mission that twice came close to failure was ending
instead in success. Credit must go to the National Aeronautics and
Space Administration's safety code, which dictates that manned
space systems must be protected as much as possible from disaster.
Computers are designed to detect and stop trouble and redundant
systems are built to replace failed ones.
   These safeguards worked July 12, when a computer detected that
an engine valve had not closed properly and ordered engine shutdown
just three seconds before liftoff.
   When Challenger finally lifted off July 29, one of the three
main engines shut down nearly three minutes early when a sensor
told a computer that it had indications of a fuel pump overheating.
The other two engines burned 86 seconds longer than planned to
propel Challenger and its crew into a safe orbit.

Associated Press Wed 07-AUG-1985 14:05                          Space Shuttle

            NASA Crew Prepare Shuttle For Homeward Journey
                          By DENNIS ANDERSON
                        Associated Press Writer
   EDWARDS AIR FORCE BASE, Calif. (AP) - Several of Challenger's
heat-resistant tiles apparently became chipped during its rocky
ascent last week, but otherwise the ship returned in good
condition, NASA said Wednesday as engineers began removing heat
sensors blamed for the launch problems.
   National Aeronautics and Space Administration spokesman Les
Reinertson said the sensors were to be shipped to the firm that
manufactures them, Rosemount of Minneapolis.
   Officials believe faulty readings by the sensors caused one
engine to shut down during launch, nearly aborting the mission as
soon as it began. The ship managed to reach a satisfactory orbit,
and the flight was so successful it was eventually extended from
seven to eight days.
   Challenger appeared to be in good condition Wednesday with the
exception of the chipped tiles and some unexplained scratches on
the orbiter's left forward and right center windows, Reinertson
said.
   ``It (the shuttle) looks pretty good,'' he said, adding the
damage incurred was normal for a shuttle mission. ``I don't think
there were any major problems from landing and re-entry.''
   Challenger, which was making the 50th manned American space
flight, sailed smoothly to Earth on Tuesday laden with a mountain
of scientic data gathered by its seven astronauts. After its 3.3
million-mile journey, the 100-ton craft landed in a cloud of dust
on a Mojave Desert dry lake bed runway.
   NASA ground crews are preparing Challenger for its return to
Kennedy Space Center in Florida. Reinertson said the shuttle would
probably be sent home Sunday.
   NASA officials are eager to verify that sensors caused the
launch problem so the shuttle Discovery can be launched Aug. 24 as
planned, with, if necessary, redesigned sensors.
   During Challenger's launch, one of three main rocket engines
turned off while the shuttle climbed toward orbit. The other
engines had to burn 86 seconds longer than planned and the crew
dumped fuel to lighten the craft.
   As a result, the shuttle orbited 46 miles below the planned
altitude, forcing researchers on the ground to redesign their
experiments.
   Challenger's $75 million array of 13 science instruments focused
on the sun, the stars and on the Earth's ionosphere. Astronauts
collected thousands of photographs, 45 hours of videotape and 230
miles of data tape.
   The crew included five scientists - geophysicist Tony England,
astronomer Karl Henize, solar physicist Loren Acton, physician
Story Musgrave, astrophysicist John-David Bartoe. Helping flight
commander Gordon Fullerton fly the craft was pilot Roy Bridges.