REM@MIT-MC@sri-unix (12/06/82)
From: Robert Elton Maas <REM at MIT-MC> Does anybody on this list know how good the pictures starfields from Voyager would be and how much maneuvering fuel it would take to aim the camera to take a bunch of pictures of nearby stars to get good paralax measurements? I wouldn't want to spend Voyager's fuel taking pictures and lose Uranus and Neptune, but if taking pictures is free except for expense of personnel and computers on Earth processing the data then I think we ought to do it. Anybody know for sure how feasible it is to use Voyager camera together with Earth or STS camera to get accurate paralax measurements of nearby stars? The current (December) issue of Sky&Telescope (on page 528) has a pair of pictures from the IECM camera-photometer on STS. One was an hour after the payload bay doors were opened on STS-2, totally ruined by streaks from debris still floating by the camera. The other was during a "quiet period" on STS-4 when stars as faint as 9th magnitude were visible in broad daylight. The latter picture seemed to be good quality. I wonder if Voyager does that well? I'm thinking it might be reasonable to send a small space telescope out on a mission of its own just for the sake of accurate parallax measurements. Perhaps after we develop the ion rocket we can send a continuously-accellerating probe out beyond our solar system in just a year or so to get much improved parallax measurements on stars hundreds of light years away. Maybe out first genuine interstellar space mission, out a lightyear or so from here, won't be to look for life but rather just to get parallax measurements on distant galaxies to compute more accurately the Hubble constant, and thus the age of the Universe. (Note that parallax measurements aren't affected by dimming by intervening gas&dust as Cephid-variable and average-bright-galaxy methods might be. They're affected only by curvature of space caused by intervening massive objects.)