A Brief Review of Spirit's Six Years of Mars Roving and Scientific Discoveries
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1007-4619 (2011) 04-651-08 Journal of Remote Sensing 遥感学报 A brief review of Spirit’s six years of Mars roving and scientifi c discoveries DI Kaichang1, GE Zhijiang2 1. State Key Laboratory of Remote Sensing Science, Jointly Sponsored by the Institute of Remote Sensing Applications of Chinese Academy of Sciences and Beijing Normal University, Beijing 100101, China; 2. China Academy of Space Technology, Beijing 100094, China Abstract: Mars rover Spirit landed in Gusev Crater on January 4, 2004. It became a stationary science platform on 26 Janu- ary 2010 after NASA’s efforts to free it from a sand trap had been unsuccessful. During its six years of exploration of the red planet, Spirit traveled 7.73 km and made signifi cant discoveries, e.g. detection of deposits of salts and minerals such as sulfur and opaline silica that only form in the presence of water. This paper presents a brief review of Spirit’s six years of Mars roving and major scientifi c discoveries. In particular, it demonstrates how planetary mapping and remote sensing technologies have been greatly supporting the mission to achieve its science and engineering goals. Key words: Mars rover Spirit, roving Mars, scientifi c discoveries, planetary mapping, remote sensing CLC number: V11 Document code: A Citation format: Di K C and Ge Z J. 2011. A brief review of Spirit’s six years of Mars roving and scientific discoveries. Journal of Remote Sensing, 15(4): 651–658 1 INTRODUCTION on 26 January 2010. By then, Spirit returned 127000 raw images and 16 color, 360-degree panoramic mosaics (NASA, 2010). The traverse Spirit, the fi rst of the two rovers of NASA’s Mars Exploration length of the mission was originally planned for 600 m to 1 km. Spirit Rover (MER) mission, was launched on 10 June 2003 from Cape actually traveled 7.73 km (odometer reading), seven to twelve times Canaveral Air Force Station, Florida, and landed in Gusev Crater longer than the planned traverse. Though Spirit won’t be roving Mars on 4 January 2004 UTC. The rover functions as a robot fi eld geolo- anymore, it will continue conducting scientifi c explorations at its fi nal gist reading the record that is contained in the rocks and soils at its resting place. For example, by tracking the radio signal from the rover landing site. The primary scientifi c objective of the MER mission long enough, scientists can get clues about the internal structure of is to explore the two landing sites on the Martian surface where Mars, i.e., to distinguish whether its core is liquid or solid. water may once have been present, and to assess past environmen- The following sections present a brief review of Spirit’s six tal conditions at those sites and their suitability for life (Squyres, et years of Mars roving and major scientifi c discoveries. In particular, al., 2004). The complete scientifi c objectives of the mission can be the paper demonstrates how planetary mapping and remote sensing found from NASA’s offi cial website (NASA, 2007). The landing site technologies have been greatly supporting the mission to achieve selected for Spirit is Gusev Crater, a fl at-fl oored crater with a diameter its science and engineering goals. of 160 km. The southern rim of Gusev is breached by Ma’adin Vallies, It should be noted that the current affi liated institutes of the au- a large branching valley that was likely cut by running water. Thus, thors are not part of the MER operations. This review is based on exploration of the landing site was anticipated to provide opportunities the relevant publications of the MER mission and some previous to study fl uvial sediments derived from the southern highlands and work of the fi rst author performed at the Mapping and GIS Labora- deposited in a lacustrine environment (Golombek, et al., 2003). tory of The Ohio State University before 2008. While its nominal mission was designed for 90 sols (a sol is a Martian day, which is 24 h 39 m 35.244 s), the rover functioned ef- 2 INSTRUMENTS AND MISSION OPERATION fectively over twenty times longer. On 1 May 2009 (sol 1893), Spirit APPROACH became stuck in soft soil at a location called “Troy”. After efforts during the past several months to free it from the sand trap had been 2.1 Scientifi c and engineering instruments unsuccessful, NASA designated the rover a stationary science platform Spirit carries an integrated suite of scientific instruments and Received: 2010-10-29; Accepted: 2011-01-04 Foundation: National High Technology Research and Development Program (863 program) of China (No. 2009AA12Z310), National Natural Science Foundation of China (No. 40871202) First author biography: DI Kaichang (1967— ), male, Ph.D., professor and doctoral advisor. His current research interests include planetary mapping and remote sensing, rover navigation and localization. E-mail: [email protected] 652 Journal of Remote Sensing 遥感学报 2011,15(4) tools called the Athena science payload. The payload includes a gamma rays produced by a 57Co source to determine splitting of mast-mounted remote sensing package, an Instrument Deploy- nuclear energy levels in 57Fe atoms. The MI uses the same CCD ment Device (IDD)-mounted in-situ package and magnets (see detectors and electronics as Pancam and can obtain high resolution Fig. 1). The remote sensing package consists of the Panoramic (30 µm/pixel) images of rock and soil surfaces. The RAT can Camera (Pancam) and the Miniature Thermal Emission Spectrom- remove 5 mm of dusty and weathered surface of a rock over a eter (Mini-TES), both supported by the Pancam Mast Assembly circular area 45 mm in diameter so that the exposed fresh mate- (PMA) (Squyres, et al., 2003). Pancam is a high-resolution color rial can be investigated in detail using the in-situ instruments. stereo pair of CCD cameras used for scientifi c investigation of the Along with Pancam and MI, each MER vehicle includes six morphology, topography, geology, etc., of the landing site. Each of engineering cameras (see Fig. 1), all of which share the same elec- its cameras (left and right) has eight multispectral channels with a tronics design and spacecraft interfaces as the Athena science cam- 400-1100 nm wavelength range (Bell, et al., 2003). Both cameras eras (Maki, et al., 2003). The Navigation Camera (Navcam) is a have an imaging area of 1024 by 1024 pixels and the fi eld of view mast-mounted stereo pair each with a 45 degree FOV and a spectral (FOV) of 16.8 degrees. Pancam has a stereo base of 30 cm, a fo- bandpass of 580—770 nm. Navcam has a stereo base of 20 cm, a cal length of 43 mm and effective depth of fi eld (DOF) of 3 m to focal length of 14.67 mm, and an effective DOF of 0.5 m to infi n- infi nity. Mini-TES is an infrared spectrometer that can determine ity. It is primarily used for navigation purposes and general site the mineralogy of rocks and soils from a distance by detecting their characterization, capable of providing 360° panoramic image mosa- patterns of thermal radiation (Squyres, et al., 2003). Mini-TES is ics and targeted images of interest. The Hazard-avoidance Cameras housed in the body of the rover at the bottom of the PMA, which (Hazcams) are mounted in stereo pairs, one pair on the front end of then acts as a periscope for it. It produces high spectral resolution the rovers’ warm electronics box (WEB) below the solar panel, and (10 cm–1) image cubes with a wavelength range of 5—29 μm, and one pair on the rear end of the WEB below the solar panel. Each angular resolution modes of 20 and 8 mrad. Hazcam assembly includes two cameras with a 124 degree FOV Once potential science targets are identified using Pancam and and 580—770 nm spectral bandpass. Hazcam has a stereo base of Mini-TES, they will be investigated in more detail using the in-situ 10 cm, a focal length of 5.58 mm, and a DOF of 0.1 m to infi nity. instruments. The IDD-mounted in-situ instruments include an Alpha The Hazcam are used for onboard hazard detection and for select- Particle-X-Ray Spectrometer (APXS), a Mössbauer Spectrometer ing near fi eld target and IDD operations. (MB), a Microscopic Imager (MI) and a Rock Abrasion Tool (RAT) (see Before launching, all of the Athena science instruments had Fig. 1) (Squyres, et al., 2003). The APXS determines the elemental undergone extensive calibration, both individually and using a set abundances of rocks and soils by exposing Martian materials to en- of geologic reference materials that were measured with all the in- ergetic alpha particles and X-rays from a radioactive 244Cm source and struments (Squyres, et al., 2003; Bell, et al., 2003). All of the MER then measuring the energy spectra of backscattered alphas and emitted engineering cameras had also been calibrated over the fl ight range X-rays. The MB is used to determine the mineralogy and oxidation of temperatures (Maki, et al., 2003). After landing, in-flight state of Fe-bearing phases. It measures the resonant absorption of calibrations have been performed for the science instruments, for Pancam(pair) Rover equipment Deck (Warm Electronics Box underneath) Navcam (pair) Low Gain Antenna UHF Pancam Mast Antenna Pancam Calibration Target Assembly Capture/Filter High Gain Antenna Megnets Hazcam (2 pairs, front and rear) Solar Arrays Instrument Deployment Device In-situ Instruments(APXS, MB, MI, RAT) Fig. 1 Spirit rover with scientifi c and engineering payload (Di and Li, 2007) DI Kaichang, et al.: A brief review of Spirit’s six years of Mars roving and scientifi c discoveries 653 example, Pancam has been regularly calibrated using refined A typical drive distance within each sol is 20 m to 50 m, oc- prefl ight-derived calibration coeffi cients, or radiance factor using casionally around 100 m.