The Mars Pathfinder Mission
Status Reports - Second Week

11 July 1997, 11:15 a.m. PDT

Commands for the next day of activities for Mars Pathfinder were not sent last night because the Pathfinder spacecraft's receiver had not been turned on in advance of the uplink session.


The lost transmission session did not impact the mission in any way, except to delay the rover and lander activities. The operations team will retransmit the same set of sequences tonight during the 8 p.m. PDT session.


11 July 1997, 2:00 p.m. PDT

After determining Pathfinder's landing site coordinates yesterday, the Mars Pathfinder navigation team today reconstructed the spacecraft's novel entry, descent and landing at a 12:00 Noon PDT briefing. The team has been analyzing data acquired in the last week to come up with this preliminary landing profile.

Pathfinder was "right on the money", within a kilometer (6/10ths of a mile) of the target landing site, said Dr. Sam Thurman, one of the entry, descent and landing team members.

The spacecraft's terminal velocity as it parachuted to the ground was about 60 meters per second (134 miles per hour). An algorithm onboard the spacecraft that controlled the retro rockets, recorded Pathfinder's speed at about 61.5 meters per second (140 miles per hour) at the time the RAD (rocket-assisted deceleration) rockets fired.

One issue of great importance to the Mars Global Surveyor team was Pathfinder's performance during descent, while it was subjected to the forces of the Martian environment. The Pathfinder navigation team reported that the spacecraft did indeed pick up some horizontal wind velocity on the order of about 13 meters per second (20 to 25 miles per hour), which was still well within the limits of the descent and landing design. That information, however, will be very useful to the Mars Global Surveyor flight team when its spacecraft begins aerobraking through the upper atmosphere of Mars in order to circularize the spacecraft's orbit.

Pathfinder next fired its retro rockets at about 98 meters (321 feet) above the ground, just slightly higher than the 90-meter (295-foot) predicted elevation target, but also well the parameters of the landing strategy. The 65-foot bridle was cut at about 21 meters (65 feet) above the ground, with just four seconds before impact.

Pathfinder's airbags -- a new component of the spacecraft never before tested for a semi-hard landing -- hit the ground at a speed of about 18 meters per second (40 miles per hour) and skidded horizontally across the landscape at about 12.5 meters per second (28 miles per hour). Pathfinder bounced about 15 meters (50 feet) high after impact, then bounced about 14 or 15 times more before coming to a stop. In all, the spacecraft bounced and rolled for about 2.5 minutes and traveled about 1 kilometer (6/10ths of a mile) before coming to a halt.

Activities for Sol 8 of Pathfinder's nearly flawless mission will include a set of commands to drive Sojourner off the large boulder, named Yogi, that it began to climb yesterday before automatically stopping itself. The rover team will send the rover new commands to reposition itself near the rock and attempt to place the alpha proton X-ray spectrometer against the rock again. The imaging team, meanwhile, released the famous "monster pan" today, a full, 360-degree color panorama of the Ares Vallis landing site.

12 July 1997, 12:45 a.m. PDT

Flight controllers reestablished radio contact with the Mars Pathfinder lander tonight and repositioned the Sojourner rover after an initial communications session did not take place because the spacecraft's computer reset itself.

Beginning at about 3 p.m. Pacific Daylight Time Friday, the flight team sent commands to the Pathfinder lander instructing the Sojourner rover to back away from a rock nicknamed Yogi.
The rover had been lodged against the rock since Wednesday evening; it was believed that commands sent Thursday to move the rover were not received by the lander because of an error in the timing of a radio uplink session.

The flight team received a signal from the Pathfinder lander's low-gain antenna at 6:47 p.m. Friday confirming that the lander received Friday's commands and was beginning to execute them. The team then expected to receive data over the lander's high-gain antenna beginning at 8:47 p.m. However, no signal was received at that time.

The team then sent a command to the Pathfinder lander via its low-gain antenna at about 9:45 p.m. instructing the lander to send a signal back to Earth. This signal was received.
Flight controllers concluded that the lander's computer must have reset itself sometime between 6:47 and 8:47 p.m. PDT Friday evening. The commands to move the rover would not have been executed, because they were scheduled to take place later.

Commands were then sent at about 11 p.m. instructing the lander to point its high-gain antenna at Earth and begin a half-hour downlink session sending engineering data reporting on the status of the lander and rover.
Commands were also sent to back the rover away from Yogi. Another command instructed the lander to take and transmit an image of the rover confirming that the repositioning had been completed.

At 12:15 a.m. PDT, the Deep Space Network station near Canberra, Australia, acquired a signal from the Pathfinder lander at the beginning of a half-hour downlink session sent via the lander's high-gain antenna. Data sent during this session indicated that the rover did in fact receive and execute commands to back it away from the Yogi rock and reposition itself on Thursday. It reexecuted these commands when they were resent Friday. In addition, an image was received at about 12:25 a.m. which showed the rover backed away from Yogi.

Friday evening marks the second time that the Pathfinder lander's computer has reset itself since its landing July 4. The flight team is not certain why the resets are taking place, but engineers noted that both incidents occurred during periods of heavy communication between the lander and rover.

Telemetry indicated that all spacecraft and rover systems are performing normally. Today is Sol 8 of the Mars Pathfinder mission.

13 July 1997, 7:00 a.m. PDT

Mars Pathfinder's lander transmitted to Earth one-third of a sweeping color panorama image, as well as engineering data to help flight controllers fine-tune spacecraft operations, during the Martian day that just ended.

The flight team expects the lander to take and transmit image frames for the other two-thirds of the color panorama tonight. Much as landscape painters often work at the same time of day over a number of days, the exposures of the Martian panorama are divided over successive days so that lighting conditions are consistent in various portions of the 360-degree image.

Pathfinder's lander also transmitted 3 megabytes of engineering data, including all data available on why the lander's computer reset itself Friday evening. The flight team is continuing work to understand and correct the problem, but it appears to be related to the behavior of software that manages interaction between activities running on the computer. The team has already sent an initial set of commands aimed at preventing future resets.

The team also sent commands for the Sojourner rover, instructing it to stand by for another day. Mission managers wanted to receive the color image panorama and engineering data before resuming rover exploration of the landing site. The team will decide later today whether to initiate any rover activities tonight.

The downlink session began at 11:15 p.m. Pacific Daylight Time Saturday night and lasted about an hour. Earth set at the landing site was at 4:27 a.m. PDT, and sunset was at 6:56 a.m. -- concluding Pathfinder's ninth day on Mars, or Sol 9.

14 July 1997, 10:00 a.m. PDT

Mars Pathfinder's lander sent about an hour's worth of data to Earth last night -- including portions of a 360-degree color panorama image -- before the lander's computer appeared to reset itself, terminating the downlink session.

Engineers are continuing to debug the reset problem, which appears to be related to software that manages how the lander's computer handles a number of different activities simultaneously. "Saturday night, we 'serialized' activities by having the lander do one thing at a time, whereas last night the lander was handling a number of activities when the reset occurred", said Brian Muirhead, Mars Pathfinder flight system manager. "Tonight we will return to a 'serialized' approach to try to avoid the possibility of a reset". The reset occurred at 1:06 a.m. Pacific Daylight Time (PDT), about halfway through a planned two-hour downlink session.

Data received during last night's downlink session indicated that the Sojourner rover is positioned against the rock nicknamed Yogi, with its alpha proton X-ray spectrometer (APXS) instrument in place to study the rock’s elemental composition. Data from the APXS should be received tonight; the science team will then decide whether to move the rover.

After rover data, the next highest priority for tonight is to complete the 360-degree color panorama image.

Last night's downlink session was during Sol 10, or Pathfinder's 10th Martian day. On Sol 10, Earth rise occurred at 3:27 p.m. PDT Sunday and sunrise was at 6:36 p.m. PDT. Earth set was at 5:07 a.m. Monday, followed by sunset at 7:35 a.m.
Tonight the flight team expects to hear from the Pathfinder lander during downlink sessions beginning at about 9 p.m. and 11 p.m. PDT.

15 July 1997, 12:00 a.m. PDT

The Mars Pathfinder flight team today reported on a very successful night of data transmission, receiving an unprecedented 90 megabits of data on the chemical makeup of a boulder nicknamed Yogi, atmospheric measurements and nearly all remaining portions of a 360-degree color panorama image of the landing site.

Last night's downlink sessions contained detailed information on the chemistry of Yogi taken by the rover after a second attempt to position its alpha proton X-ray spectrometer against the rock. The new data also included measurements of the aerosol content of the Martian atmosphere, which was used in parallel with new Hubble Space Telescope images of Mars to characterize changes in regional and global weather patterns in the last three weeks.

Recent incidents in which the Pathfinder lander's computer reset itself were discussed by Glenn Reeves, flight software team leader. According to Reeves, computer resets have occurred a total of four times during the mission -- on July 5, 10, 11 and 14. The flight team has attempted to avoid future resets by instructing the computer to handle one activity at a time -- "serializing" activities -- rather than juggling a number of activities at once.

The team continues to troubleshoot the problem by testing all of the sequences leading up to reset in JPL's Mars Pathfinder testbed; considering changes in the flight software that would allow for immediate recovery if the flight computer were to reset itself; and modifying operational activities to minimize data loss if a reset should occur again. "In a sense, the reset itself is not harmful because it brings us back into a safe state", said Reeves. "But it does cause a disruption of the operational activities".

Among the science highlights, the Pathfinder mineralogy team presented new information about Barnacle Bill, a very roughly textured rock, and Yogi, a much larger boulder nearby, which was successfully measured last night.

Yogi, low in quartz content, appears to be more primitive than Barnacle Bill, "having not gone through the cooking that Barnacle Bill and other andesites have gone through", said Dr. James Greenwood, University of Tennessee, a member of the mineralogy science team. Although these observations are very preliminary, Yogi appeared to be more like the common basalts found on Earth. The next rock to be studied is "Scooby Doo", followed by others, including "Half Dome", "Wedge", "Shark" and "Flat Top", all located in a different region of the landing site. Some are near the lander petal on which Sojourner flew to Mars.

Observations from the Earth-orbiting Hubble Space Telescope revealed a lot of surface-atmospheric transport activity. A dust storm detected in Vallis Marineris just prior to Pathfinder's landing, for instance, had all but vanished within two weeks according to new Hubble images, noted Dr. Steven Lee, University of Colorado, a Hubble investigator. Some of the dust from that regional storm had diffused to the Pathfinder landing site, which was consistent with recent Pathfinder atmospheric opacity measurements.

In observations taken between May 18 and July 11, the amount of dust near the Pathfinder landing site had nearly tripled. "There's obviously a lot of very rapid transport going on here, with some of the dust diffusing toward the landing area", Lee said. "This is consistent with Pathfinder observations on the surface".

The increase in atmospheric dust appears to be diminishing the amount of cloudiness, Lee added. Clouds observed near the southern polar hood had begun to decrease in the most recent Hubble images as the dust diffused throughout the southern hemisphere. The Hubble team estimated that these clouds were relatively low, hovering around 15 to 16 kilometers (9 to 10 miles) above the surface, because the tips of some Martian volcanoes could be seen peeking through the cloud tops.

On Pathfinder's 11th Martian day -- or Sol 11 -- Earth rise at the Martian landing site was at 4:07 p.m. Pacific Daylight Time on Monday, July 14, followed by sunrise at 7:16 p.m. PDT. The flight team radioed commands to the Pathfinder lander beginning at 7:40 p.m. PDT. Data were downlinked from Pathfinder's lander from 9:02 to 9:35 p.m. PDT using the lander's low-gain antenna; this session included the spectrometer data on Yogi. A second downlink session, on the lander's high-gain antenna, began at 1:20 a.m. and ran until 5:10 a.m. PDT, with a half-hour break in the middle while the antenna was adjusted; this session included the new portions of the color panorama image. Earth set was at 5:46 a.m. and sunset was at 8:15 a.m. PDT.

16 July 1997, 9:00 a.m. PDT

The Sojourner rover moved away from the rock nicknamed Yogi and headed toward a rock dubbed Scooby Doo during Mars Pathfinder's 12th Martian day, or Sol 12, which just concluded.

The rover moved a total of 3.6 meters (about 12 feet), and has about 2 to 3 meters (7 to 10 feet) to go to reach Scooby Doo. On the way between the two rocks, the rover's alpha proton X-ray spectrometer (APXS) instrument will be taking readings of Martian soil. The science team expects for the APXS instrument to take readings of Scooby Doo on Sol 14 -- equivalent to Thursday night and Friday morning, July 17-18.

Also during the past Martian day, the lander's Imager for Mars Pathfinder (IMP) instrument captured pictures of a Martian sunrise, atmospheric opacity and the lander's windsocks. The imager is also expected to take pictures shortly of a sunset and Mars' moon Phobos.

During Sol 12, Pathfinder's lander sent a total of 65 megabits of data to Earth. All systems are functioning normally. On this Martian day, Earth rise was at 4:47 p.m. Pacific Daylight Time on Tuesday, July 15; sunrise was at 7:56 p.m. PDT; Earth set was at 6:26 a.m. PDT Wednesday, July 16; and sunset was at 8:54 a.m. PDT.

17 July 1997, 11:00 a.m. PDT

Mars Pathfinder engineers reported a day of flawless operations of the lander and Sojourner Rover on Mars with the end of the mission's 13th day on Mars this morning, and also noted that they have found and are in the process of fixing a software bug that had caused the lander's computer to reset itself four times in recent days.

"The resets on the lander computer were caused by a software task that was unable to complete in the allotted time", said Flight Director Brian Muirhead. "We found that the task was being cut short because it had not been given high enough priority to run through to completion. Basically, we just need to add one instruction to the computer software to raise the priority of that task".

The problem was reproduced and isolated in testing at JPL. Further tests and verification will be completed today and tomorrow, with radio transmission of a software "patch" to change the lander's software scheduled for Saturday, Muirhead said.

Overnight, the Pathfinder team received all of the planned 58 megabits of data expected from the lander, along with the first of eight image sectors that will be combined to create a so-called "super-pan" high-resolution color panorama of the Martian terrain surrounding the spacecraft. The rest of the images will be transmitted back to Earth over the next several days.

A new "rover movie" created from time-lapse images taken by the lander was returned overnight. It shows Sojourner moving 2.5 meters (about 8 feet) and closing in on the whitish rock dubbed Scooby Doo. During the next Martian day, Sol 14, Rover drivers at JPL will bring the vehicle closer to the rock so Sojourner's alpha proton X-ray spectrometer can be placed against the rock.

On this Martian Day, Sol 13, Earth rise was at 5:27 p.m. yesterday, sunrise was at 9:35 p.m., Earth set was at 7:06 a.m. and sunset was at 9:33 a.m.


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


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Updated: July 23 '97

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