Instrument Information |
|
IDENTIFIER | urn:nasa:pds:context:instrument:mvic.nh::1.0 |
NAME |
MULTISPECTRAL VISIBLE IMAGING CAMERA |
TYPE |
IMAGER |
DESCRIPTION |
######################################################################## ######################################################################## REQUIRED READING: - Reuter et al. (2005) [REUTERETAL2005] - Reuter et al. (2007) [REUTERETAL2007] - SOC Instrument Interface Control Document (ICD) ######################################################################## ######################################################################## The MVIC description was was adapted from Reuter et al. (2005) [REUTERETAL2005], the MVIC section of the SOC Instrument ICD (provided in the documentation with this archive), Reuter et al. (2007) [REUTERETAL2007] (also provided with this archive), and the New Horizons website. Instrument Overview =================== MVIC is an imager that operates at both visible and near-infrared wavelengths using seven separate Charge-Coupled Device detectors (CCDs). Four CCDs have color filters (methane, red, blue and near-infrared) for producing color maps and three CCDs have panchromatic filters for observations where maximum sensitivity to faint light levels is required. In all cases, the light passes from the telescope through a filter and is focused onto the CCDs. MVIC is integrated with another instrument, LEISA, into a composite instrument named RALPH, which supplies A/D conversion, command and data handling, and power to both MVIC and LEISA. Specifications -------------- NAME: MVIC (Multispectral Visible Imaging Camera) DESCRIPTION: Imaging camera PRINCIPAL INVESTIGATOR: Alan Stern, SwRI WAVELENGTH RANGE: (Note 1) FIELD OF VIEW: 100 x N mRad (Note 2); 100 x 2.6 mRad (Note 3) ANGULAR RESOLUTION: 0.02 mRad/pixel WAVELENGTH RESOLUTION: See filter bandpasses (Note 1) Note 1: See Filters section below for Wavelength ranges and filter bandpasses. Note 2: Time-delay integration (color and two panchromatic arrays). The length of the scan determines the dimension of the scan denoted by N. Note 3: Pan frame array only. General Description ------------------- MVIC uses two large format (5024x32 pixel) CCD arrays to provide panchromatic hemispheric maps of Pluto at a double-sampled spatial resolution of 1 km by 1 km or better. Four additional 5024x32 CCDs provide hemispheric maps in blue, red, Near IR and narrow band methane color channels. These 6 arrays all operate in Time Delay Integration (TDI aka pushbroom) mode to increase sensitivity. In addition to the TDI arrays, MVIC has a 5024x128 pixel frame transfer array. For each of the arrays, the 12 pixels at either end of the rows are not opically active. Scientific Objectives ===================== Hemispheric panchromatic maps of Pluto and Charon at a resolution better than 0.5 km/pixel Hemispheric 4-color maps of Pluto and Charon at a resolution better than 5 km/pixel Search for and map atmospheric hazes at a vertical resolution better than 5 km/pixel High resolution panchromatic maps of the terminator region Panchromatic, wide phase angle coverage of Pluto, Charon, Nix, and Hydra Panchromatic stereo images of Pluto and Charon, Nix, and Hydra Orbital parameters, bulk parameters of Pluto, Charon, Nix, and Hydra Search for rings Search for additional satellites Detectors ========= MVIC comprises seven independent CCD arrays on a single-substrate focal plane. It uses two of its large format (5024x32 pixels i.e. 32 rows each 5024 pixels wide) CCD arrays, operated in TDI mode, to provide panchromatic images. Four additional 5024x32 CCDs, combined with the appropriate filters and also operated in TDI mode, provide the capability of mapping in blue, red, near-IR and narrow-band methane channels. TDI operates by synchronizing the parallel transfer rate of each of the CCDrows to the relative motion of the image across the surface of the detector. In this way, very large format images are obtained as the spacecraft scans the FOV across the surface of a target. The presence of 32 rows increases the effective integration time by that same factor, providing high signal-to-noise measurements. The measured spacecraft rotation rate can be fed back to the instrument to optimize the frame transfer rate. That is, after a scan has been initiated, the spacecraft determines the actual rotation rate and sends that information to RALPH, which uses it to calculate the frame rate that minimizes smear in the along-track direction. MVIC always produces image data in correlated double-sample (CDS) mode; that is, the reset level is subtracted from the integrated level and the difference is returned as the image. Electronics =========== The RALPH control electronics comprise three boards: the detector electronics (DE) board; the command and data handling (C&DH) board; the low voltage power supply (LVPS) board. These are contained within an electronics box (EB) mounted directly on the spacecraft, and operate essentially at the spacecraft surface temperature, which is near ambient. The DE board provides biases and clocks to both MVIC and LEISA focal planes, amplifies the signals from the arrays and performs the A/D conversion of the electrical charge of each pixel to a digital number with 12 bits of resolution. The C&DH board interprets the commands, performs the A/D conversion of the low-speed engineering data and provides both the high-speed image data interface and the low-speed housekeeping data interface. The LVPS converts the 30V spacecraft power to the voltages required by RALPH. In a long-duration mission such as New Horizons, reliability of the electronics is of paramount importance, particularly for a core instrument that addresses all major mission objectives. To ensure that RALPH is robust, almost all of the electronics are redundant. RALPH can operate on two separate sides (side A or B) which have very few components in common. The only common elements are: 1) the relays that choose whether side A or side B is to be powered, 2) The arrays themselves and 3) the interface to the spacecraft. However, the spacecraft interface has two identical circuits and is inherently redundant. For MVIC, the potential single point failure mode of the arrays is mitigated by dividing the six TDI arrays into two groupings, each containing two color CCDs and one panchromatic CCD. The first grouping comprises a pan band and the red and CH4 channels. The second grouping comprises the other pan band and the blue and NIR channels. If either group should fail, the other would still be able to meet the science requirement of observations in two color bands and one panchromatic band. Filters ======= From Reuter et al. (2007) _Bandpass__ Filter designation 400 - 975nm Panchromatic (PAN) 400 - 550nm Blue 540 - 700nm Red 780 - 975nm NIR 860 - 910nm CH4 For more details see the individual filter transmission curves in the /CALIB/ directory. Optics ====== See description above. Also: The FOV of a single MVIC pixel is 20x20 microradian^2. The panchromatic (pan) channels of MVIC will be used to produce hemispheric maps of Pluto and Charon at a double-sampled spatial resolution of 1 km^2 or better. The static FOV of each of the TDI arrays is 5.7 degrees x 0.037 degrees. In addition to the TDI arrays, MVIC has a 5024x128 element, frame transfer panchromatic array operated in staring mode, with an FOV of 5.7 degrees x 0.15 degrees. The primary purpose of the framing array is to provide image data for optical navigation of the spacecraft. Operational Modes ================= RALPH-MVIC modes are intertwined with RALPH-LEISA modes. See Reuter et al. (2007) [REUTERETAL2007], Section 7.0 'IN-FLIGHT INSTRUMENT OPERATION' for details. Calibration =========== See Reuter et al. (2007) [REUTERETAL2007], especially sections 5 and 6. Measured Parameters =================== Radiance; errors less than one DN as of 20.April 2007. See Reuter et al. (2007) [REUTERETAL2007] section 6.0 COMBINED 'PRE-LAUNCH AND IN-FLIGHT INSTRUMENT CALIBRATION RESULTS' for more details. |
MODEL IDENTIFIER | |
NAIF INSTRUMENT IDENTIFIER |
not applicable |
SERIAL NUMBER |
not applicable |
REFERENCES |
Reuter, D., A. Stern, J. Baer, L. Hardaway, D. Jennings, S. McMuldroch, J.
Moore, C. Olkin, R. Parizek, J. Scherrer, J. Stone, J. VanCleeve, and L. Young,
Ralph: a visible/infrared imager for the New Horizons Pluto/Kuiper Belt
Mission, SPIE Int. Soc. Opt. Eng., vol. 5906, 2005. Reuter, D.C., S.A. Stern, J. Scherrer, D.E. Jennings, J. Baer, J. Hanley, L. Hardaway, A. Lunsford, S. McMuldroch, J. Moore, C. Olkin, R. Parizek, H. Reitsma, D. Sabatke, J. Spencer, J. Stone, H. Throop, J. Van Cleve, G.E. Weigle, and L.A. Young, Ralph: A Visible/Infrared Imager for the New Horizons Pluto/Kuiper Belt Mission, Space Sci. Rev., Volume 140, Numbers 1-4, pp. 129-154, 2008. |