Mars Exploration Rovers Project

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Microscopic Imager

Microscopic Imager Diagram 640 x 480, 53 kilobytes Diagram opens in a new window.

The Athena Microscopic Imager (MI) is a high-resolution imaging system mounted on the Instrument Deployment Device (IDD) mounted low and extending forward on each MER rover. The MI camera body is identical to the ones used by Pancam, and MI has the same radiometric performance characteristics of Pancam imagers. The field of view of both instruments is 1024x1024 pixels in size. There is a single, broad-band filter on the MI, so imaging with the Microscopic Imager is monochromatic. To contribute to the achievement of the science objectives of the MER missions, the Microscopic Imager will:

• Image fine-scale morphology of natural surfaces (see images below),
• Image fine-scale texture and reflectance of abraded surfaces,
• Aid in the interpretation of data gathered by other instruments by imaging areas examined by them at high spatial resolution.

Microscopic Imager Lens Barrel Close-up Courtesy Jim Bell, Cornell University 700x500, 80 kilobytes

The MI optics employ a simple, fixed-focus design at f/15 that provides ±3 mm depth-of- field at 30-µm/pixel sampling. The field of view is therefore 31x31 mm at the working distance. The focal length is 20 mm, and the working distance is 63 mm from the front of the lens barrel to the object plane.

The spectral bandpass of the MI optical system is 400-680 nm. At best focus, the modulation transfer function of the optics is at least 0.35 at 30 lp/mm over this bandpass. Radiometric calibration of the Microscopic Imager will be performed with a relative (pixel-to-pixel) accuracy of <=5%, and an absolute accuracy of <=20%. The signal to noise ratio will be at least 100 for exposures of >=20% full well over the spectral bandpass and within the calibrated operating temperature range (-55ºC to +5ºC). IPS Peer Review Mars Exploration Rover The MI will be mounted on the IDD, allowing it to be placed against surfaces that can also be examined by the other Athena instruments. The IDD will have a minimum controllable motion along a science target's surface normal vector of 2±1 mm RMS, allowing it to image a rough surface in a sequence of images. After placing the MI in position for imaging, the motion of the IDD damps down to an amplitude of less than 30 microns (i.e., less than one MI pixel) within 15 seconds. Whenever the MI is not in use, the MI optics are protected from contamination by a transparent cover. The cover is opened only for MI imaging sequences. A contact sensor attached to the MI will be used to detect rock and other hard surfaces, to ensure accurate positioning and to protect the MI from accidental damage.

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Images

The following images are simulated MI images (at 20-microns/pixel) of various rocks and Martian meteorites. Click the image to view a larger version. Images open in a new window.

Images open in a new window

Jim Bell's Astronomy Magazine Image Page features several stereoscopic images of the lunar surface similar to those the MI will collect. The lunar surface images are 80-µm per pixel, with a field of view (FOV) of about 70x70 mm. The MI has an FOV of 31x31 mm, and 30-µm per pixel resolution, giving the MI about slightly less than half the FOV but twice the resolution.

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Contact Information

For more information, contact:

Ken Herkenhoff
U.S. Geological Survey, Astrogeology Team
2255 N. Gemini Dr., Flagstaff, AZ, 86001
Phone: (928) 556-7205
FAX: (928) 556-7014
E-mail: kherkenhoff@usgs.gov

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