Conference 7.286::space

Flight Status Report 
Friday, 24 January 1997

	At 1:00 p.m. on Wednesday, Surveyor's flight computer activated  
a 53-Watt heater in the Mars Orbiter Camera that will bake the 
instrument's epoxy structure with the goal of removing residual 
moisture. Without a bakeout period, the moisture in the camera's tube-
like structure will leak into space at a slow rate and cause its 
length to gradually change. As a consequence, this tiny, slow-rate 
change in the structure's length would result in a gradual shift in 
the focus of the camera. The goal of the 14-day bakeout period is to 
remove all of the moisture at once and stabilize the focus of the 
camera.

	Later in the afternoon on Wednesday, the flight team commanded 
Surveyor to perform the first of three solar array "wiggle tests" that 
occurred this week. Once per day on Wednesday, Thursday, and Friday, 
the gimbal joint holding the -Y panel to the spacecraft was commanded 
to "wiggle" the panel back and forth several times over a period of 84 
seconds. During the tests, the -Y panel inner hinge moved by 8 degrees 
before returning to its pre-test position. 

	Similar to the five "wiggle tests" performed in December, the 
Wednesday test was performed with the solar panels in the normal 
orientation used during the cruise phase of the mission. On Thursday 
and Friday, the tests were performed with the solar panels rotated 
into a position representative of that used during an engine firing 
and aerobraking, respectively.

	The flight team examined telemetry transmitted back to Earth to 
study the nature of the vibrations in the spacecraft that resulted 
from the "wiggling." The data will provide valuable insight into 
determining the best method to clear the broken damper arm that is 
wedged in the hinge joint holding the panel to the spacecraft. This 
wedged condition is keeping the -Y panel 20.5 degrees from its proper 
position.

	One option under study is to combine a "wiggle test" with a small 
firing of Surveyor's main rocket engine. The idea is that the wiggling 
will move the solar panel and allow the rocket engine to provide the 
force needed to dislodge the damper arm from the hinge joint. However, 
no decision has been made at this time.

	After a mission elapsed time of 78 days from launch, Surveyor is 
17.52 million kilometers from the Earth, 125.97 million kilometers 
from Mars, and is moving in an orbit around the Sun with a velocity of 
30.35 kilometers per second. This orbit will intercept Mars on 
September 12th, 1997. All systems on the spacecraft continue to be in 
excellent condition.


---------------------------------------
Status report prepared by:
 
Office of the Flight Operations Manager
Mars Surveyor Operations Project
NASA Jet Propulsion Laboratory
California Institute of Technology
Pasadena, CA 91109
---------------------------------------


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Flight Status Report 
Friday, 31 January 1997

	Early Monday morning, flight controllers sent several commands to 
Surveyor that deactivated the Mars Orbiter Camera's 53-Watt bakeout 
heater. This heater was activated on Wednesday, January 22nd to remove 
residual moisture in the camera's graphite epoxy structure. If the 
bakeout had not been performed, the moisture in the camera's tube-like 
structure would have slowly leaked into space and caused its length to 
gradually change. As a consequence, this tiny, slow-rate change in the 
structure's length would have resulted in a gradual shift in the focus of 
the camera during science operations. The goal of the bakeout  was to 
remove all of the moisture at once in order to stabilize the focus of the 
camera.

	Originally, the bakeout was scheduled to last for 60 days. This 
duration was subsequently reduced to 14 days last Wednesday when data 
from the camera suggested that the structure contained significantly less 
moisture than predicted. Upon request from the camera team, the flight 
operations manager made the decision to terminate the bakeout after only 
six days. The concern is that baking the camera for longer than necessary 
would be detrimental to the camera's focusing capability. 

	In several weeks, the camera will image stars over a one-week 
period for the purpose of acquiring focus calibration images. These 
images will be compared to the star images taken before bakeout in order 
to assess the best focus settings for the camera.

	Other activities this week included a two-hour radio-science 
calibration that occurred Thursday morning, just after midnight. This 
test involved using the spacecraft's ultra-stable oscillator to control 
the frequency or "tone" of Surveyor's radio transmissions to the Earth.

	Later on Thursday, flight controllers sent a command that activated 
a flange heater located near Surveyor's main rocket engine. The heater 
will gradually increase the pressure of the nitrogen tetroxide inside the 
oxidizer tank. As a consequence, the increase in oxidizer pressure will 
improve the efficiency of the propellant during the second trajectory 
correction maneuver. This maneuver is currently scheduled for March 20th.

	After a mission elapsed time of 85 days from launch, Surveyor is 
19.29 million kilometers from the Earth, 116.49 million kilometers from 
Mars, and is moving in an orbit around the Sun with a velocity of 29.83 
kilometers per second. This orbit will intercept Mars on September 12th, 
1997. All systems on the spacecraft continue to be in excellent 
condition.

---------------------------------------
Status report prepared by:
 
Office of the Flight Operations Manager
Mars Surveyor Operations Project
NASA Jet Propulsion Laboratory
California Institute of Technology
Pasadena, CA 91109
---------------------------------------


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Flight Status Report 
Friday, 7 February 1997

	Today, the flight team sent a command to Surveyor to activate the 
Mars Orbiter Camera. Over the weekend, the camera team will collect 
temperature data from the instrument in order to determine the best focus 
setting for a focus check test that will be performed on Tuesday, 
February 11th. 

	Earlier in the week, the flight team completed calibration 
activities on the gyroscopes in the inertial measurement unit. These 
gyroscopes are devices that provide critical data to the flight computers 
regarding Surveyor's pointing orientation in space. Each one of the three 
gyroscopes on the spacecraft has a primary and backup data channel. 

	Over the course of a several day period, the spacecraft team 
examined data from the backup gyroscope channels in order to understand 
the slight variations between the in-flight performance and the 
performance as specified by the manufacturer. The knowledge of these 
minor variations were incorporated into Surveyor's flight software. This 
activity was performed to improve the spacecraft's ability to maintain a 
proper orientation in the event that the backup gyroscope channels are 
used.

	Throughout this past week, the Magnetometer science instrument has 
also been active. The data collected during the week will provide the 
Magnetometer team with an opportunity to conduct further calibrations on 
the instrument. In addition, the data will provide the team with an 
opportunity to study the solar wind. This "wind" is a stream of protons 
and electrons that are constantly blown out from the Sun at a speed of 
100,000 kilometers per second.

	After a mission elapsed time of 92 days from launch, Surveyor is 
21.51 million kilometers from the Earth, 107.49 million kilometers from 
Mars, and is moving in an orbit around the Sun with a velocity of 29.31 
kilometers per second. This orbit will intercept Mars on September 12th, 
1997. The spacecraft is currently executing the C4 command sequence, and 
all systems continue to be in excellent condition.

---------------------------------------
Status report prepared by:
 
Office of the Flight Operations Manager
Mars Surveyor Operations Project
NASA Jet Propulsion Laboratory
California Institute of Technology
Pasadena, CA 91109
---------------------------------------

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Mars Global Surveyor                       
Flight Status Report
Friday, 14 February 1997

On Tuesday, the Surveyor spacecraft rotated to a position that pointed the
Mars Orbiter Camera at a cluster of stars called the Pleiades. Over the
course of an hour, the camera imaged stars within the cluster. These images
were used by the camera team to determine the focus of the narrow-angle
camera following the bakeout period that ended two weeks ago.

During that five-day bakeout period, a 53-Watt heater was used to remove
residual moisture from the camera's graphite epoxy structure. This moisture
affects the camera's focus. Preliminary results from this week's activity
indicates that additional bakeout will not be necessary. Over the next two
weeks, the camera will image the Pleiades on four separate opportunities to
allow the camera team to make adjustments to the focus settings.

On Wednesday, the spacecraft was commanded to spin in the opposite direction
for a period of three hours. Under normal conditions during the journey to
Mars, Surveyor's high-gain antenna is pointed at the Earth, and the
spacecraft slowly spins in the clockwise direction as seen from the Earth.
During the three hours, the spacecraft spun in a counter- clockwise
direction to allow the spacecraft team to calibrate the gyroscopes. These
devices provide information to Surveyor's flight computers regarding the
spacecraft's pointing orientation in space.

Today, the flight team transmitted the C5 sequence to Surveyor. C5 contains
commands that will control the spacecraft for the next four weeks. The first
activities in C5 will start on Monday, February 17th.

After a mission elapsed time of 99 days from launch, Surveyor is 24.30
million kilometers from the Earth, 98.95 million kilometers from Mars, and
is moving in an orbit around the Sun with a velocity of 28.78 kilometers per
second. This orbit will intercept Mars on September 12th, 1997. The
spacecraft is currently executing the C4 command sequence, and all systems
continue to be in excellent condition.

---------------------------------------
Status report prepared by:

Office of the Flight Operations Manager
Mars Surveyor Operations Project
NASA Jet Propulsion Laboratory
California Institute of Technology
Pasadena, CA 91109
---------------------------------------

Mars Global Surveyor
Flight Status Report 
Friday, 21 February 1997

        Today, in an activity similar to the one that occurred last week, 
the Surveyor spacecraft rotated to a position that pointed the Mars 
Orbiter Camera at a cluster of stars called the Pleiades. Over the course 
of an hour, the camera imaged stars within the cluster. Images from 
today's opportunity, combined with three image sets that will be taken 
between February 24th and February 28th, will allow the camera team to 
determine settings to control the instrument's focus.

        Other major events this week included a complete memory read-out of 
Surveyor's on-board flight computers on Monday. During this activity, the 
flight team commanded the spacecraft's computers to transmit the contents 
of its memory banks back to Earth. The read-out was performed to allow 
the flight team to verify the values of critical flight software 
parameters that control the spacecraft. Because some of these parameters 
are periodically updated, the results of the memory read-out were entered 
into a tracking system that provides a historical record of the changes. 
Monday's activity was only the second time during the mission that the 
memory has been completely read out.

        After a mission elapsed time of 106 days from launch, Surveyor is 
27.71 million kilometers from the Earth, 90.93 million kilometers from 
Mars, and is moving in an orbit around the Sun with a velocity of 28.25 
kilometers per second. This orbit will intercept Mars on September 12th, 
1997. The spacecraft is currently executing the C5 command sequence, and 
all systems continue to be in excellent condition.

---------------------------------------
Status report prepared by:

Office of the Flight Operations Manager
Mars Surveyor Operations Project
NASA Jet Propulsion Laboratory
California Institute of Technology
Pasadena, CA 91109
---------------------------------------

Flight Status Report 
Friday, 28 February 1997

	On Monday, Wednesday, and Friday of the week that began on February 
24th, the Surveyor spacecraft rotated to a position that allowed the Mars 
Orbiter Camera to obtain images within a cluster of stars called the 
Pleiades. Images were gathered over the course of one hour on each day's 
opportunity. These images, combined with the images obtained on February 
21st, will allow the camera team to determine settings to control the 
instrument's focus.

	Late in the afternoon on Friday, the spacecraft experienced a minor 
glitch with the star scanner. Normally, this device constantly scans a 
set of reference stars in deep space. These distant stars serve as fixed 
reference points that allow the spacecraft to determine its proper 
pointing orientation relative to the Earth and Sun. This process is 
called attitude control and is not related to the camera's star imaging 
for focus determination purposes.

	This glitch occurred during Friday's playback of Mars Orbiter 
Camera data from Surveyor's recorders. At that time, the star scanner 
began misidentifying stars. As a consequence, the flight team transmitted 
a command to the flight software to reset the portion of the attitude 
control software that controls the star scanner. After several hours, all 
conditions returned to normal.

	Although the cause of the glitch has not yet been determined, the 
flight team suspects that the star scanner was fooled by sunlight 
reflecting off of dust particles in the vicinity of the spacecraft. In 
order to further investigate this event, a playback of spacecraft 
engineering data recorded during the glitch will occur later this week.

	After a mission elapsed time of 113 days from launch, Surveyor is 
31.76 million kilometers from the Earth, 83.40 million kilometers from 
Mars, and is moving in an orbit around the Sun with a velocity of 27.74 
kilometers per second. This orbit will intercept Mars on September 12th, 
1997. The spacecraft is currently executing the C5 command sequence, and 
all systems continue to be in excellent condition.

---------------------------------------
Status report prepared by:
 
Office of the Flight Operations Manager
Mars Surveyor Operations Project
NASA Jet Propulsion Laboratory
California Institute of Technology
Pasadena, CA 91109
---------------------------------------

Flight Status Report 
Friday, 7 March 1997

	On Monday, the on-board command sequence controlling Surveyor 
executed a test called the "Solar Array Feather." During the several-hour 
test, the solar arrays were rotated back and forth several times in a 
similar fashion to the motion that a person makes when rotating the wrist 
joint.

	This activity was performed for the benefit of the Magnetometer 
science team. The test simulated the rotation of the solar arrays that 
will occur as the arrays automatically track the Sun during Mars mapping 
operations. Because the Magnetometer sensors sit at the end of the solar 
arrays, the data collected from the test will allow the science team to 
determine the effect of the solar array rotation on the quality of their 
data.

	On Tuesday, the flight team loaded new parameters to Surveyor's 
attitude control software. These parameters deal with the performance of 
the star scanner that controls the spacecraft's ability to point at 
targets in space. With this parameter update, the spacecraft will be able 
to point its science instruments at objects with better accuracy than 
previously possible.

	Later on Tuesday, the Ka-band communications team accomplished a 
major milestone in their experiment. Over a several hour time period, an 
antenna at the Goldstone tracking station recorded data transmitted 
simultaneously from Surveyor's X-band and Ka-band transmitters. Normally, 
the spacecraft utilizes the 25-Watt, X-band transmitter for communicating 
with the Earth. The main difference between the two signals is that the 
1-Watt, Ka-band transmitter operates at a frequency near 32 gigaHertz 
versus 8 gigaHertz for X-band.

	An analysis of the experiment indicated that no disagreements 
existed between the X-band and Ka-band data for all 12 million data bits 
observed on Tuesday. This positive result marks the first verified data 
transmission by an interplanetary spacecraft using a Ka-band signal. The 
result affirms a long-held belief that the use of Ka-band signals can 
allow a spacecraft to transmit information at faster data rates with 
transmitters that consume much less power.

	After a mission elapsed time of 120 days from launch, Surveyor is 
36.46 million kilometers from the Earth, 76.39 million kilometers from 
Mars, and is moving in an orbit around the Sun with a velocity of 27.23 
kilometers per second. This orbit will intercept Mars on September 12th, 
1997. The spacecraft is currently executing the C5 command sequence, and 
all systems continue to be in excellent condition.

---------------------------------------
Status report prepared by:
 
Office of the Flight Operations Manager
Mars Surveyor Operations Project
NASA Jet Propulsion Laboratory
California Institute of Technology
Pasadena, CA 91109
---------------------------------------

Flight Status Report 
Friday, 14 March 1997

	On Monday of this week, the flight team loaded new parameters to 
Surveyor's attitude control software. These parameters deal with the 
alignment of the Inertial Measurement Unit. This device contains three 
gyroscopes that provide the flight computers with critical information 
regarding the spacecraft's pointing orientation in space. The new 
parameters, combined with the new parameters for the star scanner that 
were loaded last week,  will enable Surveyor to point its science 
instruments at objects with better accuracy than previously possible.

	Today marked the first day since the launch of both Mars Pathfinder 
and Mars Global Surveyor that Pathfinder's distance to Mars was less than 
Surveyor's. However, because the two spacecraft are on different types of 
flight paths to Mars, they did not physically fly past each other. At the 
time of closest approach, Pathfinder and Surveyor were separated by 4.7 
million kilometers. Pathfinder was launched after Surveyor, but will 
reach Mars first because it is traveling on a shorter, more direct flight 
path.

	This week was a relatively quiet week as the flight team prepared 
for next week's trajectory correction maneuver. This engine firing will 
refine Surveyor's flight path to Mars and will take place on Thursday, 
March 20th at 10:00 a.m. PST.

	After a mission elapsed time of 127 days from launch, Surveyor is 
41.78 million kilometers from the Earth, 69.86 million kilometers from 
Mars, and is moving in an orbit around the Sun with a velocity of 26.74 
kilometers per second. This orbit will intercept Mars on September 12th, 
1997. The spacecraft is currently executing the C5 command sequence, and 
all systems continue to be in excellent condition.

---------------------------------------
Status report prepared by:
 
Office of the Flight Operations Manager
Mars Surveyor Operations Project
NASA Jet Propulsion Laboratory
California Institute of Technology
Pasadena, CA 91109
---------------------------------------

Flight Status Report 
Friday, 21 March 1997

	On Wednesday, the flight team transmitted the C6 sequence to 
Surveyor. This sequence contains commands that will control the 
spacecraft for the next four weeks. C6 became active on Thursday at 6:00 
a.m. PST. 

	The first major event in C6 occurred at 10:00 a.m. PST on Thursday. 
At that time, the onboard flight computer commanded the spacecraft's main 
rocket engine to fire for six seconds in order to make minor corrections 
to Surveyor's flight path. During this trajectory correction maneuver, 
the main engine burned a propellant combination of hydrazine fuel and 
nitrogen tetroxide oxidizer. In total, the spacecraft expended 
approximately 1.4 kilograms of propellant.

	Immediately before the six-second burn was performed, Surveyor 
ignited eight of its 12 attitude-control thrusters for 20 seconds. These 
tiny thruster rockets are normally used to stabilize the spacecraft 
during main engine firings. The initial, 20-second thruster firing 
settled the liquid in the spacecraft's tanks to ensure a smooth flow of 
propellant to the more powerful main rocket engine that was used to 
perform the correction maneuver.

	At this time, the navigation team is busy analyzing the accuracy of 
yesterday's trajectory correction maneuver. However, preliminary results 
from the accelerometer onboard the spacecraft show that the engine firing 
provided a velocity change of 3.875 meters per second. This value was 
within 0.5% of the predicted change of 3.857 meters per second.

	Yesterday's maneuver was the second in a series of four trajectory 
correction maneuvers that are designed to refine the spacecraft's flight 
path to Mars. The first maneuver occurred shortly after launch last 
November. The third and fourth are currently scheduled for April 21st and 
August 25th, respectively.

	After a mission elapsed time of 134 days from launch, Surveyor is 
47.69 million kilometers from the Earth, 63.84 million kilometers from 
Mars, and is moving in an orbit around the Sun with a velocity of 26.27 
kilometers per second. This orbit will intercept Mars on September 12th, 
1997. The spacecraft is currently executing the C6 command sequence, and 
all systems continue to be in excellent condition.
-----------------------------------------------------

Flight Status Report 
Friday, 28 March 1997

	No major activities occurred onboard the Mars Global Surveyor 
spacecraft this week. Meanwhile, at the Jet Propulsion Laboratory in 
Pasadena, Surveyor's navigation team has completed their preliminary 
assessment of the trajectory correction maneuver that took place on March 
20th. This short firing of the spacecraft's main rocket engine resulted in 
a velocity change of 3.875 meters per second and refined Surveyor's 
flight path to Mars.

	Initial analysis provided by the navigation team indicates that the 
spacecraft performed the maneuver with an accuracy of greater than 99%. 
Consequently, the spacecraft is now on a flight path that will come 
within 630 kilometers of the Martian surface at the point of closest 
approach on September 12th. Additional trajectory correction maneuvers 
scheduled for April 21st and August 25th will reduce this approach altitude 
to 500 and 380 kilometers, respectively.

	After a mission elapsed time of 141 days from launch, Surveyor is 
54.12 million kilometers from the Earth, 58.29 million kilometers from 
Mars, and is moving in an orbit around the Sun with a velocity of 25.82 
kilometers per second. This orbit will intercept Mars on September 12th, 
1997. The spacecraft is currently executing the C6 command sequence, and 
all systems continue to be in excellent condition.

---------------------------------------
Status report prepared by:
 
Office of the Flight Operations Manager
Mars Surveyor Operations Project
NASA Jet Propulsion Laboratory
California Institute of Technology
Pasadena, CA 91109
---------------------------------------

Flight Status Report 
Friday, 11 April 1997

	This week, the Mars Global Surveyor science team received an 
unexpected bonus from the Sun due to a solar flare eruption that took 
place on Monday. Eruptions of solar flares occur when disturbances deep 
within the Sun's interior cause streams of electrically charged atomic 
particles to be ejected from the solar surface. These charged particles 
move through the solar system at speeds in excess of 1,000,000 kilometers 
per hour.

	In order to allow the science team to study this event, the flight 
team sent commands to Surveyor that enabled the spacecraft to record 
solar flare data gathered from the Magnetometer science instrument. These 
commands activated the spacecraft's data recorders late Wednesday 
afternoon, about half a day before the stream of charged particles from 
Monday's eruption reached Surveyor. Although past occurrences of solar 
flares have both disrupted space communications and damaged spacecraft, 
Monday's eruption was relatively mild in comparison. The Mars-bound 
Surveyor spacecraft sustained no damage from the solar flare.

	Late Thursday afternoon, the navigators on the project canceled the 
trajectory correction maneuver that was planned for later this month. 
This maneuver would have refined the flight path to Mars by slightly 
altering the spacecraft's speed and velocity. However, analysis showed 
that this month's maneuver involves a velocity change of only 40 
millimeters per second (less than one-tenth of a mile per hour). The 
maneuver was canceled because with such a small velocity change, the 
errors in executing the maneuver are comparable to the size of the 
maneuver. 

	This canceled maneuver would have been the third of four planned 
maneuvers during the journey to Mars. The first two occurred in November 
1996 and March 1997. The fourth trajectory correction maneuver will take 
place on August 25th, 1997.  

	Yesterday marked the halfway point in the journey to Mars with 
respect to time of flight. As of April 10th, Surveyor has completed 154 of 
the 308 days required to reach the red planet. The halfway point in terms 
of distance between the Earth and Mars occurred last week on Monday, 
March 31st. This difference in halfway dates arises from the fact that the 
positions of the two planets constantly change during the spacecraft's 
journey to Mars.

	After a mission elapsed time of 155 days from launch, Surveyor is 
68.43 million kilometers from the Earth, 48.55 million kilometers from 
Mars, and is moving in an orbit around the Sun with a velocity of  24.98 
kilometers per second. This orbit will intercept Mars 153 days from now, 
slightly after 6:00 p.m. PDT on September 11th (01:00 UTC, September 12th). 
The spacecraft is currently executing the C6 command sequence, and all 
systems continue to be in excellent condition.

---------------------------------------
Status report prepared by:
 
Office of the Flight Operations Manager
Mars Surveyor Operations Project
NASA Jet Propulsion Laboratory
California Institute of Technology
Pasadena, CA 91109
---------------------------------------

Flight Status Report 
Friday, 18 April 1997

	No major mission activities occurred this week onboard the Mars 
Global Surveyor spacecraft. Back at the Jet Propulsion Laboratory in 
Pasadena, California, the project management has made a decision not to 
attempt any more efforts to free debris that is currently keeping the 
-Y-side solar array slightly out of position. This solar panel is currently 
deployed and fully functional, but is 20.5 degrees from its proper 
position. 

	The flight team believes that the position discrepancy was caused 
when a damper shaft in the array's deployment mechanism broke shortly 
after launch. This damper is a device that was installed to minimize the 
mechanical shock of deployment by slowing the motion of the array during 
deployment. The flight team theorizes that the broken shaft caused the 
damper arm to wedge into the hinge joint connecting the solar panel to 
the spacecraft.

	An important aspect of this position discrepancy is that the solar 
panels will be used at Mars not only to produce electrical power, but 
also to help the spacecraft attain its final mapping orbit. Over the 
course of a four-month period following Mars orbit insertion, Surveyor 
will be dipped into the upper Martian atmosphere on every orbit. During 
these atmospheric passes, air resistance generated by the solar panels 
will slow the spacecraft and gradually lower its orbit. Surveyor will use 
this "aerobraking" technique to lower the high point of its orbit from an 
initial 56,000 kilometer altitude to just under 400 kilometers. 

	For the last few months, the flight team has been considering 
several options to free the debris and allow the panel to latch and lock 
into its proper position. One idea involved a short firing of Surveyor's 
main rocket engine to provide a small force to dislodge the damper arm. 
However, such efforts will not be necessary because an extensive analysis 
has indicated that aerobraking with the -Y solar panel slightly out of 
position is feasible with a few minor modifications to the original plan. 

	One of the minor changes involves rotating the panel into a 
position where the front side will face into the air flow instead of the 
back side. This orientation will keep the unlatched panel from folding up 
on itself when it encounters the air flow during aerobraking. Because the 
front side contains the silicon cells that produce electricity, it is 
more fragile than the back side and cannot tolerate as much heating from 
the air flow. As a result, the flight plan will be modified so that 
Surveyor aerobrakes at a slightly slow pace than previously planned.

	After a mission elapsed time of 162 days from launch, Surveyor is 
76.20 million kilometers from the Earth, 44.32 million kilometers from 
Mars, and is moving in an orbit around the Sun with a velocity of  24.59 
kilometers per second. This orbit will intercept Mars 146 days from now, 
slightly after 6:00 p.m. PDT on September 11th (01:00 UTC, September 12th). 
The spacecraft is currently executing the C6 command sequence, and all 
systems continue to be in excellent condition.

---------------------------------------
Status report prepared by:
 
Office of the Flight Operations Manager
Mars Surveyor Operations Project
NASA Jet Propulsion Laboratory
California Institute of Technology
Pasadena, CA 91109
---------------------------------------

Mars Global Surveyor
Flight Status Report 
Friday, 25 April 1997

	Last Friday afternoon, the flight team transmitted the C7 sequence 
to Surveyor. This sequence became active at 7:00 a.m. PDT on Monday, 
April 21st and contains commands that will control the spacecraft for the 
next 28 days.

	Late in the evening on Monday, Surveyor transmitted 1.5 gigabytes 
of recorded data back to Earth. This data was collected by the 
Magnetometer science instrument two weeks ago during the solar flare 
eruption. The playback of the data took five hours to complete and 
represents nearly 52 hours of recorded science. On Tuesday, the 
spacecraft repeated the five-hour data transmission for redundancy 
purposes.

	No other major activities occurred this week. After a mission 
elapsed time of 169 days from launch, Surveyor is 84.32 million 
kilometers from the Earth, 40.49 million kilometers from Mars, and is 
moving in an orbit around the Sun with a velocity of  24.23 kilometers 
per second. This orbit will intercept Mars 139 days from now, slightly 
after 6:00 p.m. PDT on September 11th (01:00 UTC, September 12th). The 
spacecraft is currently executing the C7 command sequence, and all 
systems continue to be in excellent condition.

---------------------------------------
Status report prepared by:
 
Office of the Flight Operations Manager
Mars Surveyor Operations Project
NASA Jet Propulsion Laboratory
California Institute of Technology
Pasadena, CA 91109
---------------------------------------

Mars Global Surveyor
Flight Status Report 
Friday, 2 May 1997

	No major activities took place this week. For the past three weeks, 
few activities have occurred because the Surveyor spacecraft has been 
configured in a quiet state for a search campaign to detect gravity 
waves. According to theoretical physics, these waves are gravitational 
disturbances emitted by all objects in the universe. However, because 
gravity is a relatively weak force, detection of these waves is almost 
impossible unless they are generated by massive objects such as black 
holes and matter at the center of the Milky Way Galaxy.

	To date, nobody has ever detected a gravity wave. If Surveyor 
encountered these waves, the spacecraft would experience an extremely 
small jolt. This tiny bumping motion would cause a tiny shift in the 
frequency of the spacecraft's radio signal transmitted to Earth. Analysis 
of the data generated by this experiment will take six months or more. 
 
	After a mission elapsed time of 176 days from launch, Surveyor is 
92.74 million kilometers from the Earth, 37.03 million kilometers from 
Mars, and is moving in an orbit around the Sun with a velocity of  23.89 
kilometers per second. This orbit will intercept Mars 132 days from now, 
slightly after 6:00 p.m. PDT on September 11th (01:00 UTC, September 12th). 
The spacecraft is currently executing the C7 command sequence, and all 
systems continue to be in excellent condition.

---------------------------------------
Status report prepared by:
 
Office of the Flight Operations Manager
Mars Surveyor Operations Project
NASA Jet Propulsion Laboratory
California Institute of Technology
Pasadena, CA 91109
---------------------------------------

Mars Global Surveyor
Flight Status Report 
Friday, 9 May 1997

	At 4:30 a.m. PDT on Thursday, the flight software onboard Mars 
Global Surveyor commanded the spacecraft into safe mode. Entry into this 
operational mode placed the spacecraft in a safe power, thermal, and 
communications configuration. This precautionary measure is taken if the 
spacecraft detects an unexpected event in one or more of its subsystems. 

	The chain of events that resulted in safe mode began Wednesday 
night. At that time, the flight team was finishing the second of two 
calibrations of Surveyor's gyroscopes. These calibrations involved 
commanding the spacecraft to rotate in various directions in order to 
ascertain the performance of the gyroscopes. Surveyor had just completed 
the calibration that involved a +Z-axis rotation when the flight software 
commanded the spacecraft into contingency mode. This mode is similar to 
safe mode, but involves fewer precautionary measures taken to safe the 
spacecraft.

	Entry into contingency mode was triggered when the direction 
to the Sun as measured by Surveyor's Sun sensors disagreed with the 
predicted direction to the Sun as calculated by the onboard flight 
software. This discrepancy in Sun position was approximately 5 degrees. 
Entry into safe mode occurred about five hours later when a flight 
software task timed out and failed to report back Surveyor's central 
processor. At this time, the flight team is identifying the software 
task that timed out. 

	The entry into contingency and safe mode resulted in the flight 
software terminating the execution of the current command sequence, 
powering off the science payload and non-essential components, and 
turning the spacecraft toward the Sun to guarantee adequate power. 
Analysis of telemetry transmitted from Surveyor over the last 24 hours 
indicates that all systems are healthy. After the exact cause of safe-
mode entry is identified and resolved, the flight team will command the 
spacecraft back into its normal operational mode. This process will 
consume at least the next few days.

	Late Thursday night, the flight team transmitted a series of 
commands to Surveyor for thermal maintenance purposes. One set of 
commands shut off the secondary set of heaters to avoid overheating the 
spacecraft's 12 attitude-control thruster rockets. The other set of 
commands changed Surveyor's pointing orientation from high-gain antenna 
pointed directly toward the Sun to antenna pointed 10 degrees away from 
the Sun. This orientation change allowed for more sunlight to maintain 
warm temperatures on the science instruments.

	After a mission elapsed time of 183 days from launch, Surveyor is 
101.43 million kilometers from the Earth, 33.90 million kilometers from 
Mars, and is moving in an orbit around the Sun with a velocity of 23.58 
kilometers per second. This orbit will intercept Mars 125 days from now, 
slightly after 6:00 p.m. PDT on September 11th (01:00 UTC, September 12th). 
Although the spacecraft is currently operating in safe mode, all systems 
are functioning properly, there are no spacecraft hardware problems, and 
there is no threat to the mission.

---------------------------------------
Status report prepared by:
 
Office of the Flight Operations Manager
Mars Surveyor Operations Project
NASA Jet Propulsion Laboratory
California Institute of Technology
Pasadena, CA 91109
---------------------------------------

Mars Global Surveyor
Flight Status Report 
Friday, 16 May 1997

	This week, flight team members concentrated their efforts on 
determining what event caused the Mars Global Surveyor spacecraft to 
enter safe mode early in the morning on May 8th. Since then, Surveyor has 
been operating in a configuration that ensures that the spacecraft has 
adequate power, thermal, and communications margins. Flight software on 
the spacecraft automatically commands entry into this safe mode if it 
detects an unexpected event in one or more of Surveyor's subsystems.

	One of the major diagnostic activities involved commanding the 
spacecraft to transmit portions of its computer memory back to Earth for 
analysis. An examination of a region of memory called the Audit Queue 
revealed that entry into safe mode occurred when a flight software task 
timed out and failed to report back to Surveyor's central processor. 

	Each software task executed by Surveyor's computer is allocated a 
certain amount of time to complete. Timeouts occur when a task fails to 
complete in the allocated time. Members of the flight team at the 
Lockheed Martin facility in Denver traced the source of this timeout to 
an infinite loop that occurred in flight software. A timeout resulted 
because infinite loops are impossible to complete.

	The infinite loop resulted from the corruption of an area of 
computer memory called the Active Script Table. This table contains a 
list of programs executed by Surveyor's central processor, and 
corresponding links to the locations in computer memory where those 
programs are stored. A software task that was executing prior to safe-
mode entry caused the infinite loop when it incorrectly updated one of 
the entries in the table by linking that entry back to itself.

	Over the last few days, engineers on the flight team reproduced the 
safe-mode entry conditions in the spacecraft simulator. Subsequent 
analysis indicates that the action that created the infinite loop is 
uncommon, but predictable. Consequently, the Flight Operations Manager 
has decided to allow the flight team to begin procedures that will return 
the spacecraft back to its normal operating state. Once recovery is 
complete, the flight team will transmit modifications to Surveyor's 
flight software that will prevent this infinite loop condition from 
occurring again. Recovery operations may begin as early as Wednesday, May 
21st.

	In other news not related to safe-mode operations, the flight 
computer powered down gyroscope #2 on Tuesday, May 13th. This power down 
occurred automatically when the electrical current used by the gyroscope 
exceeded a preset limit. Gyro #2's functions were automatically assumed 
by Gyro #1 and #3, the transition was smooth, and there is no performance 
degradation with respect to Surveyor's ability to point at targets in 
space. The powered-down gyroscope will be reactivated after normal 
operations recommence. 
 
	After a mission elapsed time of 190 days from launch, Surveyor is 
110.33 million kilometers from the Earth, 31.07 million kilometers from 
Mars, and is moving in an orbit around the Sun with a velocity of 23.29 
kilometers per second. This orbit will intercept Mars 118 days from now, 
slightly after 6:00 p.m. PDT on September 11th (01:00 UTC, September 12th). 
Although the spacecraft is currently operating in safe mode, all systems 
are functioning properly, and no spacecraft hardware problems exist that 
pose a threat to the mission.

---------------------------------------
Status report prepared by:
 
Office of the Flight Operations Manager
Mars Surveyor Operations Project
NASA Jet Propulsion Laboratory
California Institute of Technology
Pasadena, CA 91109
---------------------------------------

Mars Global Surveyor
Flight Status Report 
Tuesday, 27 May 1997

	Shortly after 9:00 p.m. PDT last Saturday, operators staffing the 
Goldstone antenna complex in the Mojave desert announced that they had 
locked up on a signal transmitted from Surveyor at a data rate of 2,000 
bits per second. This milestone marked the transition out of safe-mode 
and back to normal operating conditions. Since early in the month, 
Surveyor's safe-mode orientation had limited the maximum data 
transmission rate to 250 bits per second or less. 

	The spacecraft automatically entered safe-mode on the morning on 
Thursday, May 7th when the onboard computer encountered an infinite loop 
in flight software. Entry into safe mode placed Surveyor in a 
configuration that guaranteed adequate power, thermal, and communications 
margins. This mode is intended to be a benign operating state favorable 
for diagnostic and recovery activities if an unexpected event occurs in 
one or more of the spacecraft's systems. 

	Recovery operations involved a multi-step process that began on 
Friday. First, the flight team sent a series of instructions to 
Surveyor's backup flight computer. These instructions initialized the 
backup computer to begin using its normal flight software rather than the 
limited software set utilized in safe mode. Then, the flight team 
commanded the backup computer to control the spacecraft while performing 
the same software initialization procedure on the Surveyor's primary 
computer.

	The next step required reestablishing the spacecraft's ability to 
point at targets in space. In safe mode, the flight computer assumes that 
its ability to find and point at targets other than the Sun has been 
compromised. Restoration of pointing capability involved commanding the 
spacecraft to rotate in a cone-shaped pattern around the Sun for several 
hours. This action allowed Surveyor's star scanner to lock-up on distant 
guide stars in space. The spacecraft determines its orientation in space 
by using these stars as reference points.

	Pointing capability was restored early Saturday evening. At that 
time, the flight team commanded Surveyor to rotate from its safe-mode, 
Sun-pointed orientation to an Earth-pointed orientation. Aiming the 
spacecraft's antenna directly at the Earth enabled Surveyor to begin 
transmitting data using any one of its standard rates of 2,000 bits
per second or faster. Early next week, the flight team will transmit 
modifications to Surveyor's flight software to prevent the infinite-loop 
condition from occurring again.    

	Surveyor would have been stable in safing for an indefinite period 
of time even if no corrective action had been taken. However, the flight 
team worked on restoring standard operations as quickly as possible 
because normal command sequences, such as those that control science 
calibration activities, are prohibited from executing in safe mode.

	After a mission elapsed time of 201 days from launch, Surveyor is 
124.64 million kilometers from the Earth, 27.15 million kilometers from 
Mars, and is moving in an orbit around the Sun with a velocity of  22.89 
kilometers per second. This orbit will intercept Mars 107 days from now, 
slightly after 6:00 p.m. PDT on September 11th (01:00 UTC, September 12th). 
All systems continue to be in excellent condition.

---------------------------------------
Status report prepared by:
 
Office of the Flight Operations Manager
Mars Surveyor Operations Project
NASA Jet Propulsion Laboratory
California Institute of Technology
Pasadena, CA 91109
---------------------------------------