As expected, NASA announced November 4 that it was ending its daily efforts to restore communications with the Mars Pathfinder lander, bringing one of the most popular robotic missions in the agency's history to a close.
     Project manager Brian Muirhead said at a press conference that more than a month of efforts to restore communications with the spacecraft had failed, making it unlikely that regular communications would ever be restored. "We will scale back our efforts to reestablish contact but not give up entirely."
     The announcement had been expected in advance, given reports to the press by Pathfinder team members that they were running out of options to try and make contact with the lander, which made its last successful communication with Earth September 27. Intermittent contact was made October 1 and 6, but full contact was never restored.
     Muirhead said that although the exact cause of the communications failure may never be known, engineers believe that the main battery on the lander failed in late September. Although the spacecraft generates power from its solar panels, it needs a battery to power systems like clocks overnight. The failure of the battery meant the clocks reset and the lander was unable to know when to power up.
     Since then, temperatures at the landing site have plummeted with the onset of autumn. The temperatures have now gotten so low, Muirhead said, that they have likely rendered the lander inoperable, making further communication impossible.
     The Sojourner rover may still be operating, however. It was programmed to go into a contingency mode and circle the lander, waiting for instructions, if it received no instructions after five days. The rover can communicate only through the lander, though, so it is not possible to contact the rover directly from Earth.
     Some mission officials hold out the slim hope that communications can be restored, perhaps when temperatures warm again next year. "Normal mission operations are over, but there is still a small chance of reestablishing a link, so we'll keep trying at a very low level," said mission manager Richard Cook. Commands will be sent to the lander every two to four weeks in the hope that the lander has somehow started working again.
     While the loss of communications was disappointing, the mission was a success far beyond the expectations of all involved. Pathfinder returned 2.6 billion bits of information, including over 16,000 images and 8.5 million temperature and wind measurements. Sojourner itself took over 500 images and made 15 chemical measurements of rocks with its spectrometer.
     The lander, designed to last just 30 days, and the rover, designed to last 7, had met all its primary objectives in the fir few weeks after landing. The mission had met all its extended mission objectives except for completing the "Super Pan" a super-high-resolution 360-degree color image of the landing site. About 83 percent of the Super Pan had been returned when communications were lost.
     Noting that efforts will still be made to contact Pathfinder, Muirhead said, "Given that, and the fact that Pathfinder is the first of several missions to Mars, we'll say 'see you later' instead of saying goodbye."

The Mars Global Surveyor spacecraft restarted its aerobraking maneuvers in the Martian atmosphere November 7, nearly a month after they were suspended because of a loose solar panel.
     The revised aerobraking plan, announced at a JPL press conference November 10, will alter the spacecraft's orbit more slowly than previous planned, delaying the mapping phase of the mission by one year.
     Under the new plan, the spacecraft will achieve its final circular orbit in March 1999, one year later than planned. The orbit will be a mirror image of the original planned orbit, passing from south or north over the Martian surface at 2pm local time, instead of north to south at the same local time.
     "From the perspective of the science instruments, the orbit will look just like the original orbit," said Glenn Cunningham, Mars Global Surveyor project manager at JPL.
     The one-year delay includes a six-month hiatus in aerobraking in mid-1998 to allow Mars to move into the correct alignment with the Sun. NASA plans to use this time to collect additional data on the planet, taking advantage of a fixed orbit that will bring the spacecraft closer to the surface than in the final mapping orbit.
     "We expect to gain some spectacular new data during this time," Cunningham said. "The spacecraft's orbit will still be elliptical during this period, with a duration of between eight to 12 hours, but at periapsis, the surface resolution will be much greater, and the lighting angles will be excellent."
     Aerobraking was called off October 12 when one of the two solar panels on the spacecraft bent unexpectedly during an aerobraking pass when the Martian atmosphere has twice the expected density. The panel had failed to latch into place after launch last year, but appeared to be fixed in place at a slight angle, making officials confident that it would survive aerobraking.
     Engineers believe a yoke designed to latch the panel into place may have cracked during launch and further damaged during the aerobraking pass last month. The solar panel has remained stable during the passes since aerobraking resumed.
     Scientists have been collecting data during the aerobraking hiatus, including new views of Olympus Mons, the tallest mountain on the planet, and closeups of Valles Marineris.

Two Russian cosmonauts conducted two spacewalks in less than a week outside the Mir space station, replacing a dead solar panel with a new model.
     On Monday, November 3, cosmonauts Anatoly Solovyov and Pavel Vinogradov removed an old solar panel from the Kvant module, which is docked at one end of the core module of the space station. The spacewalk took about six hours.
     The spacewalkers encountered problems when trying to return to the station at the end of the spacewalk, however. The outer hatch of the airlock in the Kvant-2 module failed to seal after it was closed, preventing the hatch from pressurizing. The spacewalkers instead used an adjoining compartment in the module as an airlock.
     Solovyov and Vinogradov made another six-hour spacewalk November 6, installing a new solar panel on the Kvant module in place of the one they removed three days earlier. The installation went well, although the panel had to be unfolded manually when the automatic deployment system failed.
     The spacewalkers noticed when they returned to the airlock that an unknown white substance had formed around the airlock, which may have contributed to its failure to seal earlier in the week. The cosmonauts cleaned off the residue and added extra locks to the hatch to seal it.
     By the following week, though, Russian officials reported that the hatch had begun to leak again, but at a slow rate. They said the hatch problem does not jeopardize the crew in any way.
     The solar panel upgrade has provided more power to the station, which is aiding the crew in resuming scientific activities as opposed to repair and maintenance work. The extra power now allows all scientific equipment to be turned back on, and Solovyov, Vinogradov, and American astronaut David Wolf are all working on experiments now.
     In addition to the solar panel repairs, the spacewalkers also installed a new valve for a Vodzhuk carbon dioxide scrubber. On the November 3 spacewalk Solovyov and Vinogradov also released a one-third scale replica of the Sputnik spacecraft, built as part of a French-Russian project involving students.
     The next Mir spacewalk is scheduled for December 5. On the spacewalk Solovyov and Wolf will install scientific experiments on the exterior of the station. A spacewalk to remove a damaged solar panel on Spektr and seal a hole in its hull from a June collision with a Progress spacecraft is being considered for January.