Hubble Space Telescope

(HST) Archive System

NASA Langley Research Center
Hampton, Virginia

Returned Hardware

Wide-Field Planetary Camera I

Background
The Wide-Field Planetary Camera I (WF/PC-I) was developed by the California Institute of Technology and built at the Jet Propulsion Laboratory (JPL). The WF/PC-I is a dual two-dimensional spectrophotometer with rudimetary polarimetric and transmission-grating capabilities. It is designed to operate at wavelengths between 1150-11000 Angstroms. Its field of view centers on the HST optical axis, thus providing the highest quality images possible.

First Servicing Mission
During the on-orbit removal of the Wide-Field Planetary Camera I (WF/PC-I), the astronauts noted that it was clean with no evidence of degradation. They also observed that the multi-layer insulation (MLI) located in the WF/PC-I bay was in immaculate condition. The crew saw no evidence of the MLI blooming against the axial instruments. They did notice, however, that the MLI on the right side had folded up a bit and covered the slot, making it difficult to put the cover in place during the installation of the mirror cover on the WF/PC-II.

Post-Retrieval Evaluations
The WF/PC-I was replaced by an updated version, WF/PC-II, which has new corrective optics. The WF/PC-I was operational at the time of replacement. Twelve high-velocity impact craters, located on the WF/PC-I radiator, were visible to the eye. The impacts include symmetrical and oblique craters with paint spall from the impact shock wave. There is also a brown line of undetermined origin on the radiator near its bolted edge. Brown stains, which surround the rivets, were evidenced prior to launch and are attributed to rivet lubrication creep. The WF/PC-I UV flood mirror, M1, was external to the WF/PC-I radiator. The UV mirror was exposed to the severity of the space environment and it suffered from blistering and peeling. The mirror lost some of the MgF² coating which was layered on top of the aluminum coating along the outer edge of the mirror. The extremely cold sensor window exhibited unusual contamination, commonly called "measles". Measles are speculated to be crystal growth around nucleation sites. Measles may also be the initial phase of a process which results in the unusual crystal-like growth features observed on LDEF and other space missions. The pickoff mirror, located in the HST interior, was observed to be in excellent condition with some evidence of dust particles.

This optical window at the entrace aperture is of special interest because it is the seal between the HST and the WF/PC-I. The inner and outer surfaces of the mirror will provide accurate, independent characterizations of the instrument and telescope contamination environments. The M1 mirror, the pickoff mirror and the aperture window will be assessed at GSFC. Further assessments of optical elements and detectors inside the instrument enclosure will be done at JPL. JPL investigations will also include assessing the mechanisms and interior mechanical components, electrical tests of the pc boards and solder joints after dissembly of the WF/PC-I, and thermal tests which will involve heat pipe performance and TEC degradation. GSFC will also participate in the electrical testing. Electrical and electronic assessment will be done using VEST. This includes IVT, EICIT, aliveness, and functional tests. Both the A and B side circuity will be tested. All results will be compared to preflight measurements.

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