Multispectral Thermal Imager Project

Significant Events

Throughout the duration of the MTI project there have been several events which have, to varying degrees, effected the functions of the satellite. LA-UR-04-3378

Calibration Lamp Failure

After ground calibrations were complete, one of the two calibration lamps on the MTI Satellite failed.  This lamp was replaced prior to launching the satellite, and the event is believed to have little to no impact on the system's performance.

Memory Module Loss

One week after the launch of the satellite, a short in the system caused the loss of one of the two memory modules aboard the satellite.  The satellite was still able to store images using the remaining memory module, however these images had to be compressed.  This caused an increase in bit errors in the images.  These errors could be identified and impacted only some of the images captured by the MTI.

Unplanned Thermal Cycles

There have been four thermal cycles caused by the shutdown of the on-board cryo-cooler.  One of these shut downs caused a fuse to blow, leading to the permanent shut-down of the Temperature and Calibration (TCAL) unit.  The loss of the TCAL unit led to the shut down of the aperture door assembly and the quick-look calibration wheel assembly.  These remained open in their default positions, which allowed for the satellite to continue collecting images.  However, it left the optical assembly open and exposed to the environment of space.  Without the use of the TCAL unit, the satellite became unable to recalibrate.  Without calibration, the accuracy of the information collected by the MTI could not be verified.  The satellite lost much of its utility for the purpose of the original mission.  The system was still able to image with all of its spectral bands, although it could no longer reliably be used to support nonproliferation efforts.  Images taken after this event were used for other applications.

Failure of On-Board Gyros

Shortly after installing the Gyro system on the MTI, it was discovered that similar gyro systems had failed on board other satellites and it was likely that the system would not last the duration of the mission.  After the gyros were shut down different techniques had to be used to point the imager at its target.  To do this scientists created algorithms using solar orientation, magnetic field alignment, and orbital position.  Following the shut down of the gyros, the daytime images that the MTI acquired continued to be accurate.  Because solar orientation is not possible on Earth's dark side the nighttime images have been more effected by this failure.

Sun Looks

Due to the complications caused by the loss of the on-board gyros, orientation of the MTI on the dark side of Earth has become difficult.  Without the use of solar orientation, the MTI has to be positioned using magnetic field alignment and orbital position.  However, when the satellite is moving over a magnetic pole it can incorrectly calculate its position.  Because of this the imager has pointed directly at the sun twice.  After each of the sun looks the MTI immediately corrected its position, so only a small area of the focal plane was affected.  The areas that were affected by the sun looks were damaged, and some lost function.

This page has paths:

This page references: