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Mars Reconnaissance Orbiter's High Resolution Imaging Science JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 112, E05S02, doi:10.1029/2005JE002605, 2007 Click Here for Full Article Mars Reconnaissance Orbiter’s High Resolution Imaging Science Experiment (HiRISE) Alfred S. McEwen,1 Eric M. Eliason,1 James W. Bergstrom,2 Nathan T. Bridges,3 Candice J. Hansen,3 W. Alan Delamere,4 John A. Grant,5 Virginia C. Gulick,6 Kenneth E. Herkenhoff,7 Laszlo Keszthelyi,7 Randolph L. Kirk,7 Michael T. Mellon,8 Steven W. Squyres,9 Nicolas Thomas,10 and Catherine M. Weitz,11 Received 9 October 2005; revised 22 May 2006; accepted 5 June 2006; published 17 May 2007. [1] The HiRISE camera features a 0.5 m diameter primary mirror, 12 m effective focal length, and a focal plane system that can acquire images containing up to 28 Gb (gigabits) of data in as little as 6 seconds. HiRISE will provide detailed images (0.25 to 1.3 m/pixel) covering 1% of the Martian surface during the 2-year Primary Science Phase (PSP) beginning November 2006. Most images will include color data covering 20% of the potential field of view. A top priority is to acquire 1000 stereo pairs and apply precision geometric corrections to enable topographic measurements to better than 25 cm vertical precision. We expect to return more than 12 Tb of HiRISE data during the 2-year PSP, and use pixel binning, conversion from 14 to 8 bit values, and a lossless compression system to increase coverage. HiRISE images are acquired via 14 CCD detectors, each with 2 output channels, and with multiple choices for pixel binning and number of Time Delay and Integration lines. HiRISE will support Mars exploration by locating and characterizing past, present, and future landing sites, unsuccessful landing sites, and past and potentially future rover traverses. We will investigate cratering, volcanism, tectonism, hydrology, sedimentary processes, stratigraphy, aeolian processes, mass wasting, landscape evolution, seasonal processes, climate change, spectrophotometry, glacial and periglacial processes, polar geology, and regolith properties. An Internet Web site (HiWeb) will enable anyone in the world to suggest HiRISE targets on Mars and to easily locate, view, and download HiRISE data products. Citation: McEwen, A. S., et al. (2007), Mars Reconnaissance Orbiter’s High Resolution Imaging Science Experiment (HiRISE), J. Geophys. Res., 112, E05S02, doi:10.1029/2005JE002605. 1. Introduction 12 August 2005 and entered Mars orbit on 10 March 2006. In this paper we describe the experiment in ways that will be [2] The High Resolution Imaging Science Experiment useful to scientists who expect to analyze the HiRISE data. (HiRISE) was selected by NASA in November 2001 and This includes a brief description of the hardware and more the Mars Reconnaissance Orbiter (MRO) was launched on detailed descriptions of measurement capabilities, sequence planning, calibration plans, and data processing. We discuss our major scientific objectives and expectations for better 1Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA. understanding the many processes that have shaped the 2Ball Aerospace & Technologies Corp., Boulder, Colorado, USA. surface of Mars. Education and public outreach plans are 3Jet Propulsion Laboratory, Pasadena, California, USA. summarized in a final section. 4Delamere Support Systems, Boulder, Colorado, USA. [3] NASA released an announcement of opportunity (AO) 5Smithsonian Institution, National Air and Space Museum, Washington, DC, USA. for several MRO science experiments in 2001, including 6NASA Ames Research Center and SETI Institute, Moffett Field, solicitation for a high-resolution imager. Science objectives California, USA. for the imager were to ‘‘Search for sites showing evidence 7U.S. Geological Survey, Flagstaff, Arizona, USA. of aqueous and/or hydrothermal activity by...observing the 8Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Colorado, USA. detailed geomorphology and stratigraphy of key locales to 9Department of Astronomy, Cornell University, Ithaca, New York, identify formation processes of geologic features suggesting USA. the presence of liquid water,’’ ‘‘Map and characterize in 10Physikalisches Institut, University of Bern, Bern, Switzerland. 11 detail the stratigraphy, geologic structure, and composition Planetary Science Institute, Tucson, Arizona, USA. of Mars surface features at many globally distributed targeted sites to better understand its complex terrain and Copyright 2007 by the American Geophysical Union. 0148-0227/07/2005JE002605$09.00 to distinguish processes of aeolian and non-aeolian trans- E05S02 1of40 E05S02 MCEWEN ET AL.: MRO’S HiRISE E05S02 port,’’ and ‘‘Explore additional ways of identifying sites periapse, and the project adapted a 255 Â 320 km orbit with with a high scientific potential for future Mars landed periapse fixed near the south pole [Zurek and Smrekar, investigations. ’’ These objectives generally followed from 2007]. At that time we decided to enlarge the telescope the recommendations of the Mars Exploration Program structure and increase the effective focal length to 12 m to Analysis Group [Mars Exploration Program Analysis achieve an instantaneous field of view (IFOV) of 1 micro- Group, 2001; Greeley et al., 2001; Zurek and Smrekar, radian, resulting in 25.5 to 32 cm/pixel imaging. In this 2007]. way we preserved meter-scale resolution (3 pixels across a [4] Originally assuming a 200 Â 400 km orbit (now meter-scale object) anywhere on Mars, provided high- 255 Â 320 km), the AO specified the following minimum frequency spacecraft pointing jitter does not significantly capabilities for the high-resolution imager: ‘‘ground reso- smear the images. lution’’ 30 cm/pixel from 200 km altitude, swath width [7] A major challenge to high-resolution imaging with a 3 km from 200 km, and signal-to-noise ratio (SNR) ground track velocity of 3.2 km/sec is how to collect ‘‘adequate for operation in a 3:00 PM local mean solar time enough photons to make a high-quality image. One option orbit.’’ We assumed that the 30 cm/pixel guideline (which is would be to fly a very large telescope, but that is difficult a ground sampling dimension, not resolution) also required to accommodate on a spacecraft with limited resources. a reasonable Modulation Transfer Function (MTF) for the Another option is to slew the spacecraft or instrument or a complete system, such as 0.1 at Nyquist (2 pixel length scanning mirror to slow down the ground velocity of the scale). Resolution of a surface feature (e.g., enabling instrument field of view; slewing the instrument is the measurement of its planimetric dimensions) depends on strategy used by the Compact Reconnaissance Imaging the contrast of the feature, SNR, and illumination angle, Spectrometer for Mars, CRISM [Murchie et al., 2007]. but a useful guideline is that 3 pixels (with 0.1 MTF and We chose to use Time Delay Integration (TDI), in which high SNR) are needed across an object to consider it each small patch of ground is imaged up to 128 times and resolved. Fewer pixels may be needed for detection of an the signals are summed to increase SNR [Delamere et al., object or feature (especially linear features), but may 2003; Dorn et al., 2004; Bergstrom et al., 2004]. The preclude more than an upper limit on dimensions, and HiRISE charge-coupled device detectors (CCDs) are 2048 may not distinguish between positive and negative relief pixels wide and 128 pixels high for TDI. We can choose to unless the object is isolated against a uniform background. use all 128 lines, or 64, 32, or 8 lines, depending on the In essence, our interpretation was that the AO was calling scene brightness, binning level, and tradeoff between SNR for the capability to measure the dimensions of 1 meter and potential smear. TDI imaging requires very precise scale objects on the Martian surface. We suspect that this stability and pointing control by the spacecraft, as described requirement metric traced, in part, from an engineering by Lee et al. [2001]. evaluation for the 2001 Mars Surveyor lander (now reborn [8] Square pixel binning is available in 6 modes: none as the Phoenix lander), that landing on a 0.33 m high object (1 Â 1), 2 Â 2, 3 Â 3, 4 Â 4, 8 Â 8, and 16 Â 16. We will could be fatal [Golombek et al., 1999], and that an object use binning when desired to reduce data volume and such as a mostly buried boulder 0.33 m high would have an increase coverage of Mars or to increase SNR. The 8 Â 8 exposed diameter of 1 m. High resolution is also essential and 16 Â 16 binning lead to saturation of well-illuminated for many science studies, but the precise resolution needed scenes and will be most useful for imaging in twilight to varies widely depending on the science objective and extend the seasonal monitoring of polar regions. We have a characteristics of the surface materials. stepped resolution strategy in which we can image with a [5] We placed a major emphasis on stereo imaging and subset of CCDs (usually in the center of our FOV) at full precision geometric corrections needed to make small-scale resolution, other CCDs with, for example, 4 Â 4 binning, topographic measurements, essential both to characteriza- and then the Context Camera, CTX [Malin et al., 2007] tion of candidate landing sites and to quantitative study of images have a pixel scale twenty times larger than full- surface processes. In addition we added a 3-color capability resolution HiRISE images and a swath width of 30 km. Thus over 20% of the swath width, because color images can help we can step out by factors of 4 and 5 in pixel scale, covering resolve ambiguities in image interpretation, such as whether progressively larger areas at lower resolution for regional brightness variations are due to topographic shading or the context. reflectivity of different surface materials, and will enable us [9] In addition to pixel binning, the data can be com- to place compositional data from other experiments into pressed from 14 to 8 bits and the 8-bit images can be further more specific geologic and stratigraphic context.
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