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Martian Spirit In A Better Mood As Battery Power Rises
Pasadena CA (JPL) Jul 15, 2008 Spirit's battery is recharging nicely now that rover planners have reduced the frequency of communications to and from the rover during the darkest days of Martian winter. Most measures of battery health are showing an increase of about 2 amp-hours in the battery state of charge (an amp-hour is equivalent to the amount of charge flowing for one hour from a current of 1 amp). The minimum state of charge has improved from 10.92 amp-hours to 12.97 amp-hours, the maximum from 16.77 amp-hours to 18.17 amp-hours, which is fairly close to the battery's full capacity of 19.5 amp-hours. Because battery energy increased sufficiently, the team added 12 minutes of remote sensing science to Spirit's to-do list for Sol 1586 (June 19, 2008). Spirit was to monitor atmospheric dust with the panoramic camera as well as dust on the panoramic-camera mast assembly and acquire seven, time-lapse movie frames in search of clouds with the navigation camera. Engineers anticipate that the additional activities will have no significant effect on the battery's state of charge. Skies remain remarkably clear. Solar array energy is up slightly, averaging 229 watt-hours (100 watt-hours is the amount of energy needed to light a 100-watt bulb for one hour). Atmospheric darkness caused by dust (known as Tau) increased by an insignificant amount, going from an average of 0.193 the previous week to 0.205 this week. The dust factor, the fraction of sunlight hitting the arrays that penetrates the dust layer, also rose insignificantly, from 0.349 to 0.352. Rover planners are generating new activity plans for Spirit only once a week to minimize uplink time and therefore the length of time the rover must stay awake. Spirit relays data to Earth only every fourth sol to minimize battery usage. In addition to estimating the amount of scattering and absorption of sunlight by atmospheric dust, Spirit received one transmission of new instructions direct from Earth to the rover's high-gain antenna on Sol 1581 (June 14, 2008). Spirit sent two transmissions of data to Earth via Odyssey on sols 1582 and 1586 (June 15 and June 19, 2008). Data from the sol 1582 downlink showed that the backup uplink on sol 1584 (June 17, 2008) was not needed and the communications link was shortened to save energy. Spirit remains healthy and all subsystems were performing as expected as of the downlink to Earth via NASA's Odyssey Mars orbiter on sol (Martian day) 1582 (June 15, 2008). Sol-by-sol summary During the past week, Spirit completed the following activities: Sol 1580 (June 13, 2008): Spirit recharged the battery and measured atmospheric opacity caused by dust (Tau) using the panoramic camera. Sol 1581: Spirit recharged the battery and received new instructions direct from Earth to the rover's high-gain dish antenna. Sol 1582: Spirit soaked up the sunlight to recharge the battery, assessed atmospheric darkness caused by dust particles with the panoramic camera, and sent data to NASA's Odyssey orbiter for transmission to Earth. Sol 1583: Spirit recharged the battery. Sol 1584: Spirit recharged the battery, surveyed atmospheric dust with the panoramic camera, and received new commands from Earth over the rover's high-gain antenna. Sol 1585: Spirit recharged the battery. Sol 1586 (June 19, 2008): Plans called for Spirit to recharge the battery, conducted remote sensing, and send data to Odyssey for relay to Earth. Odometry: As of sol 1578 (June 11, 2008), Spirit's total odometry remained at 7,528.0 meters (4.7 miles). Related Links Mars Rovers at JPL Mars Rovers at Cornell Mars News and Information at MarsDaily.com Lunar Dreams and more
Spirit Biding Time
Pasadena CA (SPX) Jul 14, 2008Spirit continues to ride out the Martian winter by doing minimal activities to conserve power. The rover conducts very light science activities every three to four Martian days, or sols, and relays data to NASA's Odyssey orbiter for transmission to Earth every 4 sols. The rest of the time, Spirit mostly sleeps. |
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