Instrument Information
INSTRUMENT_ID OSIWAC
INSTRUMENT_NAME OSIRIS - WIDE ANGLE CAMERA
INSTRUMENT_TYPE FRAME CCD REFLECTING TELESCOPE
INSTRUMENT_HOST_ID RO
INSTRUMENT_DESC
The instrument was provided by the OSIRIS consortium led by the
    principal investigator Dr. Horst Uwe Keller.
 
    The OSIRIS consortium have the following members:
 
    MPS         Overall responsibility and project management, system
                engineering, interfaces, Focal Plane Assemblies, CCDs
                and Readout Boards, HK Boards, integration  and
                qualification of  E-Boxes, harnesses, system
                integration, high level software, NAC & WAC system
                calibration, QA, mission operations
 
    LAM         NAC telescope, camera integration and qualification
                WAC optical bench, camera
 
    UPD         Integration and qualification, shutter mechanisms and
                shutter electronics, Front Door Mechanisms (mechanisms
                for NAC and WAC)
 
    IAA         Mechanism Controller Board
 
    INTA        Filter Wheel Mechanisms, E-Box Power Converter Module,
                NAC & WAC CRB Power Converter Modules
 
    RSSD        Data Processing Unit
 
    IDA         Mass memory, low level software and data compression
 
    DASP        NAC & WAC Filters
 
    UPM         Thermal and structural analysis, NAC MLI, WAC FPA MLI
 
    For detailed instrument description please see the Space Science
    Review Paper (OSIRIS_SSR) included in the dataset.
 
 
    Instrument Overview
    ===================
 
    The OSIRIS camera system consists of a narrow angle camera (NAC)
    and a wide angle camera (WAC)
 
 
    ==============================
    The narrow angle camera (NAC):
    ==============================
 
    The NAC uses an off axis three mirror optical design. The off
    axis design was selected in order to minimize the stray light
    reaching the CCD (The NAC has a proven stray light attenuation
    of better than 1.0e-9). The optical beam is reflected of the
    three mirrors (M1 - M3) before passing through a double filter
    wheel, a mechanical shutter mechanism and an anti radiation
    plate (ARP) before reaching the CCD.
 
    The NAC optical path:
                                      (target object)
                                            /
    Focal Plane -----                      /
     ARP          ---         M2      /   /   /  Aperture
      Shutter      ---       ----        /
       Filter2      ---       /\        /
        Filter1      ---     /  \      /
                       \    /    \    /
                        \  /      \  /
                         \/        \/
                        ----      ----
                         M3        M1
 
    Basic NAC parameters:
    ---------------------------------------------------------------
    | Optical design                 |     3-mirror  off-axis     |
    | Angular resolution             |     18.6 urad px-1         |
    | Focal length                   |     717.4 mm               |
    | Mass                           |     13.2 kg                |
    | Field of view                  |     2.20 x 2.22deg         |
    | F-number                       |     8                      |
    | Spatial scale from 100 km      |     1.86 m px-1            |
    | Typical filter bandpass        |     40 nm                  |
    | Wavelength range               |     250nm - 1000nm         |
    | Number of filters              |     12                     |
    | Estimated detection threshold  |     18 mV                  |
    ---------------------------------------------------------------
 
 
    The double filter wheels allows the NAC to place a refocusing
    plate together with an optical filter in the optical beam. The
    NAC is equipped with two types of refocusing plates allowing
    optimum focus at 4km and 1.2km
    respectively.
 
    The NAC is equipped with the following optical filters:
 
 -------------------------------------------------------------------
 |  Name   |  Wavelength  |  Bandwidth  |  Peak  |  Objective      |
 |         |     [nm]     |    [nm]     |   [%]  |                 |
 -------------------------------------------------------------------
 |  FFP-UV       600          > 600        > 99   BBAR coated      |
 |                                                plate to allow   |
 |                                                use of wheel 2   |
 |  FFP-IR       600          > 600        > 99   BBAR coated      |
 |                                                plate to allow   |
 |                                                use of wheel 1   |
 |  Neutral      640           520         5.0    Neutral density  |
 |                                                filter           |
 |  NFP-Vis      600         > 600        > 98    Refocusing lens  |
 |                                                for near-nucleus |
 |                                                imaging,         |
 |                                                BBAR coated      |
 |  Far-UV       269.3        53.6        37.8    Surface spectral |
 |                                                reflectance      |
 |  Near-UV      360.0        51.1        78.2    Surface spectral |
 |                                                reflectance      |
 |  Blue         480.7        74.9        74.6    Surface spectral |
 |                                                reflectance      |
 |  Green        535.7        62.4        75.8    Surface spectral |
 |                                                reflectance      |
 |  FFP-Vis      600         600         >90      Refocusing lens  |
 |                                                for near-nucleus |
 |                                                imaging,         |
 |                                                BBAR coated      |
 |  Orange       649.2        84.5        92.4    HMC orange       |
 |                                                filter;          |
 |                                                surface spectral |
 |                                                reflectance      |
 |  Hydra        701.2        22.1        87.4    Water of         |
 |                                                hydration band   |
 |  Red          743.7        64.1        96.0    Surface spectral |
 |                                                reflectance      |
 |  Ortho        805.3        40.5        69.8    Orthopyroxene    |
 |  Near-IR      882.1        65.9        78.4    Surface spectral |
 |                                                reflectance      |
 |  Fe2O3        931.9        34.9        81.6    Iron-bearing     |
 |                                                minerals         |
 |  IR           989.3        38.2        78.1    IR Surface       |
 |                                                reflectance      |
 -------------------------------------------------------------------
 
 -------------------------------------------------------------
 |  Name    |  Thickness  |  Wheel  |  Position  |  Encoder  |
 |          | centre [mm] |         |            |   [DN]    |
 -------------------------------------------------------------
 |  FFP-UV        4.41         1           1          14     |
 |                                                           |
 |                                                           |
 |  FFP-IR        5.15         2           1          14     |
 |                                                           |
 |                                                           |
 |  Neutral       4.64         1           8          11     |
 |                                                           |
 |  NFP-Vis       4.18         1           3           4     |
 |                                                           |
 |                                                           |
 |                                                           |
 |  Far-UV        4.50         2           5           2     |
 |                                                           |
 |  Near-UV       4.68         2           6           7     |
 |                                                           |
 |  Blue          4.67         2           4           1     |
 |                                                           |
 |  Green         4.64         2           3           8     |
 |                                                           |
 |  FFP-Vis       5.00         1           2          13     |
 |                                                           |
 |                                                           |
 |                                                           |
 |  Orange        4.73         2           2          11     |
 |                                                           |
 |                                                           |
 |                                                           |
 |  Hydra         4.72         2           7           4     |
 |                                                           |
 |  Red           4.68         2           8          13     |
 |                                                           |
 |  Ortho         4.69         1           5           2     |
 |  Near-IR       4.75         1           4           7     |
 |                                                           |
 |  Fe2O3         4.73         1           6           1     |
 |                                                           |
 |  IR            4.74         1           7           8     |
 |                                                           |
 -------------------------------------------------------------
 
    For details on the shutter mechanism see the Shutter section
    below.
 
    For details on the CCD please see the CCD section below.
 
 
 
 
 
 
    ============================
    The wide angle camera (WAC):
    ============================
 
    The WAC uses an off axis two mirror optical design. The off axis
    design was selected in order to minimize the strayligh reaching
    the CCD (The NAC has a proven strayligh attenuation of better
    than 1.0e-8). The optical beam is reflected of the two mirrors
    (M1 & M2)before passing through a double filter wheel, a
    mechanical shutter mechanism, an anti radiation plate (ARP)
    before reaching the CCD.
 
 
 
    The WAC optical path:
    ---------------------
 
                                      (target object)
                                            /
                                           /
                              M2      /   /   /  Aperture
                             ----        /
                              /\        /
                             /  \      /
             Filter1       ---   \    /
            Filter2       ---     \  /
           Shutter       ---       \/
          ARP           ---       ----
         Focal Plan   -----        M1
 
 
    Basic WAC parameters:
    ---------------------
 
      ---------------------------------------------------------------
      | Optical design                 |     2-mirror  off-axis     |
      | Angular resolution             |     101 urad px-1          |
      | Focal length                   |     140(sag)/131(tan)      |
      | Mass                           |     9.48 kg                |
      | Field of view                  |     11.34 x 12.11deg       |
      | F-number                       |     5.6                    |
      | Spatial scale from 100 km      |     10.1 m px-1            |
      | Typical filter bandpass        |     5 nm                   |
      | Wavelength range               |     240nm - 720nm          |
      | Number of filters              |     14                     |
      | Estimated detection threshold  |     13 mV                  |
      ---------------------------------------------------------------
 
    The WAC camera does not have refocusing plates so the two WAC
    filter wheels each have a filter position with no filter mounted.
    So the typical WAC observation uses either the filter combination
    (empty + filter) or filter + empty)
 
    The WAC is equipped with the following optical filters:
 
 --------------------------------------------------------------------
 |  Name   |  Wavelength  |  Bandwidth  |  Peak  |  Objective       |
 |         |     [nm]     |    [nm]     |   [%]  |                  |
 --------------------------------------------------------------------
 |  Empty                                           Empty position  |
 |                                                  to allow        |
 |                                                  the use of      |
 |                                                  filter wheel 2  |
 |  Empty                                           Empty position  |
 |                                                  to allow        |
 |                                                  the use of      |
 |                                                  filter wheel 1  |
 |  UV245        246.2         14.1        31.8     Continuum       |
 |                                                  surface spectral|
 |                                                  reflectance     |
 |  CS           259.0          5.6        29.8     CS gas emission |
 |  UV295        295.9         10.9        30.4     Continuum for OH|
 |  OH-WAC       309.7          4.1        26.0     OH emission from|
 |                                                  the vicinity of |
 |                                                  the nucleus     |
 |  UV325        325.8         10.7        31.6     Continuum for OH|
 |                                                  surface spectral|
 |                                                  reflectance     |
 |  NH           335.9          4.1        23.6     NH gas emission |
 |  UV375        375.6          9.8        57.3     Continuum for CN|
 |                                                  surface spectral|
 |                                                  reflectance     |
 |  CN           388.4          5.2        37.4     CN gas emission |
 |  Green        537.2         63.2        76.8     Dust continuum  |
 |  NH2          572.1         11.5        60.9     NH2 gas emission|
 |  Na           590.7          4.7        59.0     Sodium gas      |
 |                                                  emission        |
 |  VIS610       612.6          9.8        83.4     Continuum for OI|
 |                                                  surface spectral|
 |                                                  reflectance     |
 |  OI           631.6          4.0        52.4     O (1D) gas      |
 |                                                  emission        |
 |                                                  for dissociation|
 |                                                  of H2O          |
 |  R            629.8        156.8        95.7     Broadband filter|
 |                                                  for nucleus and |
 |                                                  asteroid        |
 |                                                  detection       |
 |                                                  (NAC redundancy)|
 --------------------------------------------------------------------
 
 ------------------------------------------------------------
 |  Name   |  Thickness  |  Wheel  |  Position  |  Encoder  |
 |         | centre [mm] |         |            |   [DN]    |
 ------------------------------------------------------------
 |  Empty                     1           1          14     |
 |                                                          |
 |                                                          |
 |                                                          |
 |  Empty                     2           1          14     |
 |                                                          |
 |                                                          |
 |                                                          |
 |  UV245       4.51          1           3           4     |
 |                                                          |
 |                                                          |
 |  CS          4.60          1           4           7     |
 |  UV295       4.75          1           5           2     |
 |  OH-WAC      4.82          1           6           1     |
 |                                                          |
 |                                                          |
 |  UV325       4.85          1           7           8     |
 |                                                          |
 |                                                          |
 |  NH          4.86          1           8          11     |
 |  UV375       4.60          2           3           8     |
 |                                                          |
 |                                                          |
 |  CN          4.61          2           4           1     |
 |  Green       4.71          1           2          13     |
 |  NH2         4.74          2           5           2     |
 |  Na          4.75          2           6           7     |
 |                                                          |
 |  VIS610      4.65          2           8          13     |
 |                                                          |
 |                                                          |
 |  OI          4.66          2           7           4     |
 |                                                          |
 |                                                          |
 |                                                          |
 |  R           4.67          2           2          11     |
 ------------------------------------------------------------
 
    =============================
    The OSIRIS mechanical shutter
    =============================
 
    Both the NAC and the WAC cameras are equipped with a mechanical
    shutter mechanism for controlling the exposure time. The
    shutter mechanism uses two blades to control the exposure.
    The first blade covers the CCD at the start of the exposure.
    when the exposure is started the first blade is accelerated
    to 1.3 m/s before the edge of the blade reaches the edge of
    the CCD. the blade edge then passes over the CCD at constant
    velocity before being decelerated to standstill after passing
    the far edge of the CCD. The end of the exposure is controlled
    by performing the same motion with a second blade that initially
    is outside the CCD surface. The second blade motion starts after
    the exposure time has passed from the start of the first blade
    motion. The full blade travel lasts 53ms. For exposure times
    shorter than 53 ms the blade motion of the two blades overlap.
    In this case the exposure is controlled by a moving slit
    (same principle as a SLR camera).
 
    During the blade motions the position is measured using a
    position encoder mounted on the drive shaft of the shutter
    motors.
 
    The minimum allowed exposure time is 10 ms and accuracy of the
    exposure is better than 5us
 
 
    ==============
    The OSIRIS CCD
    ==============
 
    The OSIRIS camera system uses 2048x2048 pixel backside
    illuminated CCD's. The CCD's are equipped with anti reflection
    coatings optimized for the UV spectral range. The CCD's are
    equipped with shielded anti-blooming control. The CCD's are
    UV sensitive down to 240nm (50% QE) and IR sensitive up to
    1000nm (6% QE). The system gain is set to ~3e- in normal
    operational mode. The readout electronics is using a dual
    14 bit ADC configuration giving an effective 16 bit system.
    The CCD's uses two readout channels (channel A and B) which
    can be used in parallel for fast readout. The CCD's can be
    read out using hardware windowing and hardware binning (1x1,
    2x2, 4x4 and 8x8). The fastest readout of a 1x1 binned fullframe
    image is 3.4s. By using windowing and binning modes this time
    can be reduced to less than 1s.
 
    OSIRIS CCD specification:
 
 --------------------------------------------------------------------
 | Item                     | Specification                         |
 --------------------------------------------------------------------
 | Source detector type     | E2V CCD42-40, non-MPP, backside       |
 |                          | illuminated,|Hafnium oxide AR         |
 |                          | coated                                |
 | Array size               | Full frame,  2048 x 2048 pixels       |
 | Serial register size     | 50 + 2k + 50;  50 extra pixel         |
 |                          |                at both ends           |
 |                          | 48 + 2k + 48   transmitted            |
 | Pixel size               | 13.5 um x 13.5 um                     |
 | No. of outputs           | 2;  either 1 sufficient               |
 | Overexposure             | Shielded anti-blooming control        |
 | Operation modes          | Clock dithering for dark              |
 |                          | current reduction for                 |
 |                          | operations at > 220 K                 |
 |                          | (optional), windowing, binning        |
 | Full well                | > 100 000 e- px-1                     |
 | System gain              | ~ 3 e- / DU                           |
 | Readout noise (CCD)      | < 7 e- rms                            |
 | Dark charge generation   | ~0.6 e- s-1 px-1  @ 180 K             |
 |                          | ~200 e- s-1 px-1  @ 293 K             |
 |                          |                (with dithering)       |
 | QE                       | 250 nm: 50 %,   400 nm: 60 %,         |
 |                          | 600 nm: 80 %,                         |
 |                          | 800 nm: 60 %, 1000 nm:   6 %          |
 | Readout rate             | 1.3 Mpx s-1;  650 kpx s-1 per channel |
 | Readout time (full frame)| 3.4 s (2 channels)                    |
 | Vertical clock rate      | 25 us per line                        |
 | Operating temperature    | 160 K < T < 300 K                     |
 --------------------------------------------------------------------
REFERENCE_DESCRIPTION Keller, H.U., et al., OSIRIS - The Scientific Camera System Onboard Rosetta, Space Sci. Rev., 128(1-4), 403-506, Feb. 2007.