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NEAR Multispectral Imager (MSI)

NSSDCA ID: 1996-008A-01

Mission Name: NEAR Shoemaker
Principal Investigator:Dr. Joseph F. Veverka

Description

The NEAR multispectral imaging system (MSI) is designed to take images at various wavelengths with the scientific objectives of mapping asteroid morphology and surface composition, determining the overall size, shape, and spin characteristics, and to search for satellites. These objectives will be executed for asteroid 433 Eros from orbit, and have been achieved for asteroid 253 Mathilde during the 27 June 1997 flyby. The imager will also be used for optical navigation. Data returned by the MSI will complement that returned by the near-infrared and x-ray/gamma-ray spectrometers in determining mineralogy of the surface rocks and dust.

The MSI has a mass of 3.7 kg, and the supporting electronics 4.0 kg. The camera is mounted on the instrument platform on the end of the craft opposite the antenna and consists of an optical system and a Si CCD focal plane unit. The optical system is made up of a five element refractive f/3.4 telescope with a 168-mm focal length and an eight position filter wheel. The filter wheel has seven color filters covering the wavelength range from visible to near-infrared (450, 550, 760, 900, 950, 1000, and 1050 nm) and one broadband filter. The color filters are chosen to optimize the identification of iron-containing silicate minerals. The broadband filter is primarily for low-light imaging and optical navigation.

The field of view is 2.25 by 2.9 degrees, equivalent to 3.9 x 5.1 km from 100 km range. The system has an electronic shutter which allows 10 millisecond to 1 second exposures, and the instrument has a 1 second frame rate. The operating temperature is -40 C to -30 C. The CCD is passively cooled and has an array of 244 x 550 pixels, of which 244 x 537 are used. Each pixel element is 16 x 27 micrometers in size, and has a resolution of 95 x 161 microradians (9.5 x 16.1 m at a range of 100 km). The CCD is sensitive to the wavelength range of 400-1100 nm and the brightness is encoded to 12 bit depth. The DPU electronics package controls the instrument and provides three-tiered compression, including a selection of lossless modes, and lookup tables for conversion from 12- to 8-bit images.

Astronomical objects will be used to calibrate the instrument performance over the course of the mission. During the 253 Mathilde flyby the imager returned over 500 pictures of the asteroid. During the approach to 433 Eros, the MSI will be used for a search for small satellite bodies. After the flyby, NEAR will be in a high orbit from which images of Eros will be taken and the satellite search continued. The orbit will be progressively lowered and the first comprehensive map will be obtained from an altitude of about 100 km with 12 m resolution. High resolution (up to 3 meters) and stereo mapping will then be done from the low 35 km orbit. The images will provide information on composition, geologic and impact history, crater distribution, surface morphology, spin rate, and color. This will allow studies of surface processes, internal structure, distribution and thickness of regolith, and the relationship of the asteroid to meteorites. In concert with the laser ranging instrument MSI will determine the size, shape, and volume of Eros and using the results of the radio science experiment the bulk density will be estimated.

Alternate Names

  • MSI
  • NEARShoemaker/MSI

Facts in Brief

Mass: 7.7 kg
Power (avg): 13.9 W

Funding Agency

  • National Aeronautics and Space Administration United States

Discipline

  • Planetary Science: Small Bodies

Additional Information

Questions and comments about this experiment can be directed to: Dr. David R. Williams

 

Personnel

NameRoleOriginal AffiliationE-mail
Dr. Joseph F. VeverkaTeam LeaderCornell Universityjfv4@cornell.edu
Dr. Guenter E. BruecknerTeam MemberUS Naval Research Laboratory
Dr. Clark R. ChapmanTeam MemberPlanetary Science Institutecchapman@swri.edu
Dr. Michael C. MalinTeam MemberMalin Space Science Systems, Incmalin@msss.com
Dr. Peter C. ThomasTeam MemberCornell University
Dr. Lucy-Ann McFaddenTeam MemberUniversity of Marylandmcfadden@astro.umd.edu
Dr. Mark S. RobinsonTeam MemberUS Geological Surveyrobinson@sirius.wr.usgs.gov
Prof. James F Bell, IIITeam MemberCornell Universityjfb8@cornell.edu

Selected References

  • Hawkins, S. E., III, et al., Multi-spectral imager on the Near Earth Asteroid Rendezvous mission, Space Sci. Rev., 82, No. 1-2, 31-100, 1997.
  • Veverka, J., et al., An overview of the NEAR multispectral imager- near-infrared spectrometer investigation, J. Geophys. Res., 102, No. E10, 23709-23727, Oct. 1997.
  • Veverka, J., et al., NEAR's flyby of 253 Mathilde: Images of a C asteroid, Science, 278, No. 5346, 2109-2114, Dec. 1997.
  • Hawkins, S. E., III, Overview of the multi-spectral imager on the Near spacecraft, Acta Astronautica, 39, No. 1-4, 265-271, 1996.
  • Thomas, P. C., et al., Eros: Shape, topography, and slope processes, Icarus, 155, No. 1, 18-37, Jan. 2002.
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