Instrument Overview
  ===================
    The High Resolution Stereo Camera (HRSC), originally developed
    for the Russian-led Mars-96 mission, was selected as part of the
    Orbiter payload for ESA s Mars Express mission. The HRSC is a
    pushbroom scanning instrument with nine CCD line detectors
    mounted in parallel in the focal plane. Its unique feature is the
    ability to obtain near-simultaneous imaging data of a specific
    site at high resolution, with along-track triple stereo, four
    colours and five different phase angles, thus avoiding any time-
    dependent variations of the observational conditions. An
    additional Super-Resolution Channel (SRC) a framing device will
    yield nested images in the metre-resolution range for detailed
    photogeologic studies. The spatial resolution from the nominal
    periapsis altitude of 250 km will be 10 m px 1, with an image
    swath of 53 km, for the HRSC and 2.3 m px 1 for the SRC.
    During the mission s nominal operational lifetime of 1 Martian
    year (2 Earth years) and assuming an average HRSC data transfer
    share of 40%, it will be possible to cover at least 50% of the
    Martian surface at a spatial resolution of d 15 m px 1. More than
    70% of the surface can be observed at a spatial resolution of d
    30 m px 1, while more than 1% will be imaged at better than 2.5 m
    px 1. The HRSC will thus close the gap between the medium- to
    low resolution coverage and the very high-resolution images of
    the Mars Observer Camera on the Mars Global Surveyor mission and
    the in situ observations and measurements by landers. The HRSC
    will make a major contribution to the study of Martian
    geosciences, with special emphasis on the evolution of the
    surface in general, the evolution of volcanism, and the role of
    water throughout Martian history. The instrument will obtain
    images containing morphologic and topographic information at high
    spatial and vertical resolution, allowing the improvement of the
    cartographic base down to scales of 1:50 000. The experiment will
    also address atmospheric phenomena and atmosphere-surface
    interactions, and will provide urgently needed support for
    current and future lander missions as well as for exobiological
    studies. The goals of HRSC on Mars Express will not be met by any
    other planned mission or instrument.
 
 
  Science Objectives
  ==================
    The HRSC directly addresses two of the main scientific goals of
    the Mars Express mission (high-resolution photogeology and
    surface-atmosphere interactions) and significantly supports
    another two (atmospheric studies and mineralogical mapping).
    In addition, the imagery will make a major contribution to
    characterising the landing site geology and its surroundings for
    the Mars Express and other Mars missions (e.g. NASA's Mars
    Exploration Rovers).
    The scientific objectives and measurement goals have been
    formulated by an international team of 45 Co-Investigators (Co-
    Is) from 10 countries under the leadership of the Principal
    Investigator (PI).
    The image data will focus on:
    - characterisation of the surface structure and morphology at
      high spatial resolution of e10 m px 1;
    - characterisation of the surface topography at high spatial and
      vertical resolution;
    - characterisation of morphological details at super-resolution
      of up to 2 m px 1;
    - terrain classification at high spatial resolution by means of
      colour imaging;   refinement of the geodetic control network
      and the Martian cartographic base;
    - characterisation of atmospheric phenomena;
    - characterisation of physical properties of the surface through
      multi-phase angle measurement;
    - observation of Phobos and Deimos.
 
 
  Investigators and Other Key Personnel
  =====================================
    Principal Investigator:  G. Neukum, FU Berlin, Germany
    Experiment Manager:      R. Jaumann, DLR Berlin, Germany
    Data Processing Manager: T. Roatsch, DLR Berlin, Germany
 
    HRSC Co-Investigators:
 
    J. Albertz, TU Berlin, Germany
    G. Bellucci, Istituto di Fisica Spazio Interplanetario (INAF),
       Italy
    J.-P. Bibring, Institut d Astrophysique Spatiale, CNRS, France
    M. Buchroithner, TU Dresden, Germany
    E. Dorrer, Universitaet der Bundeswehr, Muenchen, Germany
    H. Ebner, TU Muenchen, Germany
    E. Hauber, Institut fuer Planetenforschung, DLR, Berlin, Germany
    C. Heipke, TU Hannover, Germany
    H. Hoffmann, Institut fuer Planetenforschung, DLR, Berlin,
       Germany
    W.-H. Ip, Max-Planck-Institut fuer Aeronomie, Katlenburg-Lindau,
       Germany
    R. Jaumann, Institut fuer Planetenforschung, DLR, Berlin, Germany
    H.-U. Keller, Max-Planck-Institut fuer Aeronomie, Katlenburg-
       Lindau, Germany
    P. Kronberg, TU Clausthal, Germany
    W. Markiewicz, Max-Planck-Inst. fuer Aeronomie, Katlenburg-
       Lindau, Germany
    H. Mayer, Universitaet der Bundeswehr, Muenchen, Germany
    F.M. Neubauer, Universitaet Koeln, Germany
    J. Oberst, Institut fuer Planetenforschung, DLR, Berlin, Germany
    M. Paetzold, Universitaet Koeln, Germany
    R. Pischel, Institut fuer Planetenforschung, DLR, Berlin, Germany
    G. Schwarz, DLR Oberpfaffenhofen,, Germany
    T. Spohn, Institut fuer Planetenforschung, DLR, Berlin, Germany
    B.H. Foing, ESA - ESTEC, Noordwijk, Netherlands
    K. Kraus, TU Wien, Austria
    K. Lumme, University of Helsinki, Finland
    P. Masson, Univ. Paris-Sud, France
    J.-P. Muller, University College London, United Kingdom
    J.B. Murray, The Open University, Buckinghamshire, United Kingdom
    G. Gabriele Ori, Universita  d Annunzio, Italy
    P. Pinet, GRGS, Observatoire de Midi-Pyrenees, France
    J. Raitala, University of Oulu, Finland
    A.T. Basilevsky, Russian Academy of Science, Moscow, Russia
    B.A. Ivanov, Russian Academy of Science, Moscow, Russia
    R. Kuzmin, Russian Academy of Science, Moscow, Russia
    M.H. Carr, US Geological Survey, Menlo Park, USA
    T.C. Duxbury, NASA-JPL, USA
    R. Greeley, Arizona State University, Phoenix, USA.
    J.W. Head, Brown University, Providence, USA
    R. Kirk, US Geological Survey, Flagstaff, USA
    T.B. McCord, University of Hawaii, USA
    S.W. Squyres, Cornell University, Ithaca, USA
    A. Inada, Kobe University, Japan
 
    HRSC Experiment Team.
 
    DLR: T. Behnke, U. Carsenty, K. Eichentopf, J. Flohrer, B. Giese,
         K. Gwinner, E. Hauber, H. Hirsch, H. Hoffmann,
         A. Hoffmeister, R. Jaumann, D. Jobs, U. Koehler, K.-D. Matz,
         V. Mertens, J. Oberst, S. Pieth, R. Pischel, C. Reck,
         E. Ress, D. Reifl, T. Roatsch, F. Scholten, G. Schwarz,
         I. Sebastian, S. Sujew, W. Tost, M. Tschentscher,
         M. Waehlisch, I. Walter, M. Weiss, S. Weifle, M. Weiland,
         K. Wesemann;
    FU Berlin: T. Denk, O. Fabel, S. van Gasselt, C. Georgi,
         S. Huber, G. Mygiakis, G. Neukum, S. Preuschmann,
         B. Schreiner, S. Werner, W. Zuschneid;
    Subcontractors: A. Zaglauer, U. Schoenfeldt, K. Eckhardt,
         J. Krieger, D, Tennef, S. Govaers, A. Kasemann, M. Langfeld
         (DLR/Anagramm), E. Rickus (Levicki microelectronic),
         J. Schoeneich (Jena-Optronik)
 
 
  Instrument Specification
  ========================
    The HRSC instrument consists of the camera unit containing the
    HRSC stereo colour scanner and the Super-Resolution Channel
    (SRC), and of the digital unit. The unique capability of the HRSC
    stereo colour scanner is to obtain quasi-simultaneously high-
    resolution images in three-line stereo, in four colours and at
    five phase angles. The combination with the SRC makes it a five-
    in-one camera:
    - the along-track acquisition of stereo imagery avoids changes
      in atmospheric and illumination conditions which so far have
      caused severe problems in the photogrammetric evaluation of
      stereo images acquired at well-separated times;
    - the triple stereo images permit robust stereo reconstruction,
      yielding Digital Terrain Models (DTMs) at a vertical resolution
      similar to the high pixel resolution of the nadir sensor, with
      10 m px 1 at 250 km altitude (periapsis);
    - the colour images enable terrain classification and provide
      information on compositional variations and surface weathering
      as a complement to the more specific (but with lower spatial
      resolution) mineralogical information obtained by the imaging
      spectrometer of Mars Express;
    - the multiphase imagery will address the physical properties of
      the Martian soil (roughness, grain size, porosity) via
      photogrammetric data evaluation by providing a second stereo
      angle triplet (in essence quintuple stereo);
    - the super-resolution imagery, nested in the broader swath of
      the scanner with a spatial resolution of 2.3 m px 1 at
      periapsis, will serve as the magnifying lens to analyse surface
      morphology at even greater detail.
 
    The HRSC stereo colour scanner is a multi-sensor pushbroom
    instrument, with nine CCD line sensors mounted in parallel
    delivering nine superimposed image swaths. Originally, it was
    developed as the HRSC instrument for the Russian Mars-96 mission.
    Two fully tested and calibrated Flight Models were prepared, and
    only minor modifications to the remaining version were required
    to satisfy the Mars Express interface requirements. The stereo
    colour scanner comprises a baffle, optics, optical bench,
    spectral filters, CCD sensors lines, sensor electronics and
    thermal control system. The technical design is defined by:
    - single-optics design;
    - CCD line arrays with 5272 pixels each;
    - nine detectors for simultaneous stereo and colour imaging,
      and for multi-phase angle measurements;
    - CCDs and sensor electronics implemented in high-reliability
      hybrid, low-noise and low-power technology;
    - implementation of the CCD-control unit in ASICs.
 
    The SRC is a framing device and uses an interline CCD detector to
    cope with the very short exposure and read-out times. It is based
    on an instrument development for the Rosetta Lander and the
    design is characterised by:
    - CCD area array interline detector with 1024 x 1032 pixels;
    - highly miniaturised and low-power detector and control
      electronics;
    - compact 3D multi-chip module technology using thin-film
      multilayer metallisation, dycostrate, plasma-etching and chip-
      on-wire technology;
    - selectable dynamic range of 8- and 14-bit per pixel;
    - internal data buffer to store eight 8-bit (or four 14-bit)
      images;
    - lightweight Maksutov-Cassegrain telescope with a focal length
      of 975 mm
 
 
  INSTRUMENT OPERATION
  ====================
    In general, the HRSC (Camera Head) and the SRC will be operated
    simultaneously. However, the Camera Head and the SRC also can be
    operated separately.
 
    The SRC can be operated
    - in the direct mode (direct input into the DU)
      In the case of joint operations with the Camera Head (CH) this
      mode requires that the 9 CCD line signals are processed by three
      of the four signal chains (which reduces the possible number of
      configurations or macro modes). The fourth signal chain is
      exclusively used for SRC.
      The SRC data is fully integrated in the basic HRSC data stream.
    - in the buffer mode
      This mode is applicable for all HRSC macro modes. Eight 8-bit or
      four 14-bit SRC images can be stored in an internal buffer. At
      the end of an imaging session these images are processed by the
      signal chain #4.
    For each of the SRC operational modes the following exposure modes
    can be selected by command:
    - spot mode: single images
    - raster mode: images taken at a predefined time distance
    - contiguous imaging: raster imaging with such a distance between
      subsequent exposures that a contiguous image strip is generated
 
    The HRSC instrument output rate is mainly defined by the scan
    frequency of the Camera Head, i.e. it changes with the S/C
    altitude. The SRC images are fully embedded in the HRSC instrument
    data stream. They reach not more than 10% in the entire data
    stream even in the contiguous mode. The HRSC data output rate is
    reduced by two measures:
    - pixel binning Each of the four signal chains can be commanded to
      sum pixels in flight and across flight direction: 1x1, 2x2, 4x4
      and 8x8 (macropixel formats). One signal chain can handle only -
      one sensor 1x1 or - up to two sensors 2x2 or - up to four
      sensors 4x4 or - up to eight sensors 8x8 or - SRC images
    - Data compression Each of the four signal chains performs in
      parallel an on-line (hardware) data compression with a modified
      JPEG algorithm. The compression rate is defined not directly but
      only through a quality factor given by command. In general we
      assume compression factors from 6..10 for nominal operations.
      The actual output at a certain time instance rate depends on the
      compression behaviour (scene contents, buffer handling of the
      hardware etc) and cannot be exactly predicted.