On the Use of Electrostrictive Actuators in Recovering the Optical Performance of the Hubble Space Telescope
- PDF / 5,076,791 Bytes
- 12 Pages / 414.72 x 648 pts Page_size
- 86 Downloads / 199 Views
ABSTRACT This paper describes the development of a space qualified active mirror-the Articulating Fold Mirror-which forms part of the scheme for recovering the optical performance of the Hubble Space Telescope. Three Articulating Fold Mirrors are incorporated into the optical train of the Jet Propulsion Laboratory's Wide Field and Planetary Camera-2, which was installed into Hubble by astronauts in December, 1993. Each Articulating Fold Mirror utilizes six electrostrictive ceramic multilayer actuators to precisely position a mirror in tip and tilt in order to correct the spherical aberration of the Hubble Space Telescope's primary mirror. Flight qualification aspects of the electrostrictive actuators are described. Pre- and postrepair images from the Wide Field and Planetary Camera, showing the effect of the optical correction, are presented.
INTRODUCTION Occasionally we encounter design situations where compact, precision actuation mechanisms are needed. This occurred recently during the development of the Wide Field and Planetary Camera-2 (WFPC2) for the Hubble Space Telescope (HST). The Wide Field and Planetary Camera was developed by the Jet Propulsion Laboratory (JPL) as the primary science instrument aboard the Hubble Space Telescope; nearly all of the images from HST are obtained using this camera (see Figure 1). The first generation Wide Field and Planetary Camera (WFPC1) was launched with Hubble in April of 1990. Shortly thereafter, images from WFPC1 revealed a serious defect in the HST optics-the celebrated spherical aberrationof the telescope's primary mirror. It was soon widely recognized that the spherical aberration flaw in the HST primary mirror could, in principle, be corrected by making a minor alteration to the optical design of the Wide Field and Planetary Camera-2, a flight spare camera (essentially a copy of WFPC1) that was nearing completion at JPL. NASA directed JPL to make the necessary changes to WFPC2, and to accelerate the development schedule such that the new camera would be completed in time to be installed into HST during the first servicing mission, planned for late 1993.
109
Mat. Res. Soc. Symp. Proc. Vol. 360 0 1995 Materials Research Society
RADIATOR OPTICAL BENCH (GRAPHITE EPOXY)
BEAM FROM HUBBLE TELESCOPE
PYRAMID MIRROR
00
FILTER ASSEMBLY (48 FILTERS) SHUTTER PICK-OFF
RELAY PRIMARY, MIRROR ,
CCD
-'rIMAGING
SSENSOR
RELAY SECONDARY MIRROR (WrITH CORECTIVE FIGURE)
MIRROR
CAMERA RELAY HEAD OPTICS ASSEMBLY ARTICULATING FOLD MIRRORS
PICKOFF MIRROR
Figure 1. The Wide Field and Planetary Camera-2. About the size of a baby grand piano, this instrument was installed into Hubble by astronauts in December, 1993, and is designed to correct the spherical aberration of the telescope's primary mirror.
PYRAMID MIRROR (AT THE HUBBLE FOCAL PLANE)
Figure 2. Optical Train. The pyramid mirror splits the incoming beam into four optical trains, each of which contains a fold mirror and a corrector mirror (about the size of a dime) where the spherical aberration is "canceled."
Three
Data Loading...
