* Astronomy

SPIRIT UPDATE: Spirit Copes with Decreasing Solar Energy - sol 881-888, July 06, 2006:

With electrical power from Spirit's solar array down to about 300 watt-hours per Martian day, or sol, the science team is able to plan only one major activity per sol and often needs to devote one sol to recharging the rover's batteries. (A hundred watt-hours is the amount of electricity needed to light one 100-watt bulb for one hour.) Spirit remains healthy and continues to make progress on the winter science campaign.

Engineers successfully uploaded half of a new flight software upgrade and planned to take advantage of overflights by NASA's Odyssey orbiter to transmit more flight software files via UHF frequencies.
The rover team created a new technique for correcting drift (changes with time) in the rover's inertial measurement unit, which affects the pointing accuracy of the miniature thermal emission spectrometer. The IMU provides roll, pitch, and yaw information to the rover. Typically, rover handlers minimise error by having the rover complete a sequence of steps known as a "get fine attitude" based on the changing position of the sun relative to the rover. The rover then takes images with the hazard avoidance and navigation cameras, which provide guidance for positioning the robotic arm and driving as well as documenting the correction. The entire process takes about one hour, which at present is roughly equivalent to a week of winter science operations. Between these updates, the rover's onboard computer keeps track of attitude changes, but error builds up in this calculation over time.
The new process involves sending a command to Spirit with the position reported by the rover after the last quick "get fine attitude," on sol 855 (May 30, 2006). Rover drivers confirmed that the rover had not moved since then by checking images from the hazard avoidance cameras. Following the usual attitude adjustment, the team planned to direct the rover to take two new images with the navigation camera and compare those to images from sol 855 as an additional means of verifying the accuracy of the adjustment.

Sol-by-sol summaries

Sol 881 (June 25, 2006): Rover handlers spent one hour transmitting flight software files to Spirit via X-band frequencies using the rover's high-gain antenna.

Sol 882: Spirit completed a "bitty cloud" search designed to look for changes in the Martian sky, a photon transfer observation to measure electronic noise (unwanted signals) picked up by CCDs (charge-coupled devices -- imaging sensors that convert light into electrical current) in the left eye of the rover's panoramic camera, and observations of ground targets and atmosphere with the miniature thermal emission spectrometer.

Sol 883: Spirit conducted a 5-hour observation of the rock target "Halley" with the Mössbauer spectrometer. The rover also conducted morning atmospheric studies.

Sol 884: Spirit completed a photon transfer observation of the right eye of the panoramic camera.

Sol 885: Plans called for Spirit to conduct atmospheric studies of the Martian sky and ground using the panoramic camera and miniature thermal emission spectrometer. The rover's schedule also included another 5-hour study of Halley with the Mössbauer spectrometer.

Sol 886: Plans called for Spirit to conduct more "bitty cloud" observations, collect remote observations of the sky and ground with the miniature thermal emission spectrometer, set the rover attitude, and calibrate the high-gain antenna.

Sol 887: Plans called for Spirit to acquire a single frame of column 21 of the "McMurdo panorama."

Sol 888 (July 3, 2006): Plans called for Spirit to recharge the batteries and make morning atmospheric studies.

Odometry:
As of sol 884 (June 28, 2006), Spirit's total odometry remained at 6,876.18 metres.

SPIRIT UPDATE: Spirit "Warms up the Engines," Continues Work on Mars - sol 874-880, June 23, 2006:

Since the beginning of Spirit's winter science campaign, the science and engineering teams have held joint meetings every few weeks to track campaign progress and come up with a strategic plan that balances engineering resources with science productivity. This week, Spirit began acquiring the 22nd column of the 27-column "McMurdo panorama" and completed the seventh of nine photon transfer calibrations - procedures designed to measure electronic noise (unwanted signals) picked up by imaging sensors that convert light into electrical current in the rover's cameras.

Spirit also conducted studies of a soil target nicknamed "Halley Brunt," which is an undisturbed exposure of bright, sparkly bits of soil near the rover's left front wheel. The work included 5 hours of examination with the alpha particle X-ray spectrometer, 10 hours of examination with the Moessbauer spectrometer, and acquisition of microscopic images.

For the first time on either rover, Spirit's battery heaters turned on at 8:15 a.m. local solar time on Mars on Sol 865 (June 9, 2006). The heaters activate automatically when local temperatures drop to about minus 19 degrees Celsius. The lowest allowable operating temperature is minus 20 degrees C.

Sol-by-sol summaries:

Sol 874 (June 18, 2006): Spirit acquired Part A of column 22 of the McMurdo panorama.

Sol 875: Spirit studied soil target "Halley Brunt" with the alpha particle X-ray spectrometer.

Sol 876: Spirit completed a photon transfer calibration of the microscopic imager. Spirit also acquired a panoramic view of a dune field called "El Dorado" and conducted remote studies using the miniature thermal emission spectrometer.

Sol 877: Spirit acquired navigation camera images of the rover's tracks and continued to make remote observations using the miniature thermal emission spectrometer. While communicating with the Odyssey spacecraft as it passed overhead, Spirit calibrated the miniature thermal emission spectrometer, took images of a sand ripple using the hazard avoidance cameras, and made observations of the sky and ground using the miniature thermal emission spectrometer.

Sol 878: Spirit completed a dust monitoring assessment of the panoramic camera's mast assembly, acquired panoramic camera images to measure atmospheric dust opacity (known as a tau measurement), and conducted sky and ground observations using the miniature thermal emission spectrometer.

Sol 879: Plans called for Spirit to complete acquisition of Part B of column 22 of the McMurdo panorama and make more observations with the miniature thermal emission spectrometer.

Sol 880 (June 24, 2006): Plans called for Spirit to take microscopic images of Halley Brunt and then switch tools to the Mössbauer spectrometer for a 10-hour study of the same target.

Odometry:
As of sol 877 (June 21, 2006), Spirit's total odometry remained at 6,876.18 metres.

SPIRIT UPDATE: Progress on Long-Term Experiments - sol 860-866, June 9, 2006:

Spirit is healthy and continues to make progress on the rover's winter science experiments. Spirit has begun work on a new "photon transfer calibration" experiment designed to measure electronic noise (unwanted signals) picked up by CCDs (charge-coupled devices -- imaging sensors that convert light into electrical current) in the rover's cameras. This week the rover conducted the calibration experiment on the panoramic camera and rear hazard-avoidance cameras.
Spirit also began an experiment to look for wind-driven changes in the Martian surface by making the first of several monthly checks, using all 13 filters of the panoramic camera, of a bright soil target nicknamed "Tyrone." In addition, that camera acquired column 18 of the "McMurdo panorama." Rover science team members prepared to have the rover remove another 2 millimetres of soil as part of a soil analysis experiment. The newly exposed soil target will be called "Progress 3."

Sol-by-sol summaries:

Sol 860 (June 4, 2006): Spirit completed 30 minutes of remote sensing and conducted the photon transfer calibration on the panoramic camera. Demonstrating that the rover is capable of multi-tasking, Spirit spent 60 minutes communicating with NASA's Mars Odyssey spacecraft as Odyssey passed overhead while Spirit also studied Martian terrain targets with the miniature thermal emission spectrometer.

Sol 861: Spirit collected images with the microscopic imager and transmitted 70 megabits of data over UHF frequencies during a morning telecommunications link with Odyssey. Spirit also checked the three-dimensional movement of the rock abrasion tool at the end of the rover's instrument arm. This process involves taking measurements from encoders, which resemble dials on a safe. The encoders tick off the distance travelled by motor shafts and convert the mechanical motion into electronic signals. The results enable engineers to check for slippage or sticking that would necessitate changes in the amount of movement needed to position the instrument as desired.

Sol 862: Spirit acquired the first part of Column 18 (a 1-by-3 mosaic) of the McMurdo panorama. The rover spent 60 minutes communicating with Odyssey as it passed overhead, while also conducting remote targeted sensing using the miniature thermal emission spectrometer.

Sol 863: Spirit acquired the second half of Column 18 (a 1-by-3 mosaic) of the McMurdo panorama and took a picture of the Martian sunset.

Sol 864: Spirit took a 13-filter colour image of the Tyrone soil target using the panoramic camera and conducted analysis of the ground and sky at different elevations using the miniature thermal emission spectrometer.

Sol 865: Spirit completed the photon transfer calibration experiment on the rover's rear hazard-avoidance cameras.

Sol 866 (June 10, 2006): Plans called for Spirit to use the rock abrasion tool to brush away a third layer of soil 2 millimetres thick from the soil target called Progress. Spirit was to spend 54 minutes on the task as part of a progressive soil brushing experiment before documenting the spot with images from the panoramic camera using all 13 colour filters.

Odometry:
As of sol 863 (June 7, 2006), Spirit's total odometry remained at 6,876.18 meters.

SPIRIT UPDATE: Spirit Perfects Pointing Parameters, Collects Images Large and Small - sol 855-859, June 1, 2006:

Since arriving at the rover's current location on the 807th sol, or Martian day, of exploration (April 10, 2006), Spirit's knowledge of its attitude relative to the sun has drifted. The rover uses an onboard computer to keep track of attitude changes, but error builds up in this measurement over time. On sol 855 (May 30, 2006), rover planners transmitted an attitude update of 1.97 degrees to correct for the drift. After the update, Spirit re-acquired images from the same location to allow the science team to accurately target future observations.

Meanwhile, Spirit continued acquisition of the "McMurdo panorama" and removed another 2 millimetres of soil as part of a layer-by-layer soil study.

Sol-by-sol summaries:

Sol 855 (May 30, 2006): Spirit completed a quick get-fine attitude, which is a procedure completed every couple of weeks to correct any error in the rover's knowledge of its attitude relative to the sun. Spirit also took a 360-degree view of its surroundings with the navigation camera and a forward-looking view through the front hazard avoidance camera. The rover conducted remote sensing with the miniature thermal emission spectrometer during the overhead pass of the Mars Odyssey spacecraft.

Sol 856: Spirit acquired column 16 (a one-by-five mosaic) of the McMurdo panorama.

Sol 857: Spirit spent 80 minutes brushing away another 2 millimetres of soil from the soil target "Progress." This layer of the study is known as "Progress 3."

Sol 858: Plans called for Spirit to take microscopic images of Progress 3, conduct remote sensing with the miniature thermal emission spectrometer during the afternoon overhead pass of the Odyssey spacecraft, and take two panoramic-camera images during the Martian sunset.

Sol 859 (June 3, 2006): Plans call for Spirit to acquire column 17 (a one-by-three mosaic) of the McMurdo panorama.

Odometry:
As of sol 857 (June 1, 2006), Spirit's total odometry remained at 6,876.18 meters.