REM%IMSSS@SU-AI.ARPA.UUCP (11/22/86)
<GA> Date: Tue, 18 Nov 86 16:40:33 cet <GA> To: SPACE@s1-b.arpa <GA> From: ESG7%DFVLROP1.BITNET@wiscvm.wisc.edu (Gary Allen) <GA> Subject: Rebuttal on TAU and further remarks on Pluto as a rogue planet <GA> My assertion that the TAU may be a boondoggle induced response from many <GA> readers. Steve Willner correctly states that the prime mission for the <GA> TAU is to measure stellar distances by parallax. Accuracy through this <GA> method can be achieved through either having a large and accurately <GA> known base leg with a telescope of modest resolution, or a short and <GA> even more accurately known base leg with a high resolution telescope. On the other hand, even with a "perfect" telescope located near Earth, curvature of space in this vicinity may invalidite the results beyond a certain accuracy. This curvature may be systematic due to the Earth and Sun etc., or a uniform granularity below a certain resolution caused by the Oort cloud. Having some telescopes way out there in flat space, where we have a large baseline hence don't need such high angular accuracy, may be useful as a check against our near-Earth observations. Therefore the TAU seems intrinsically valuable and irreplacable, thus worthy of consideration. As you say, we must weigh the relative merits and costs with finite monetarily and manpower resources. But I dismiss your claim that TAU is a boondoggle from the outset. <GA> Also on my admittedly crazy idea about Pluto being a rogue planet, ... If as somebody said Pluto and Neptune are currently in stable resonance, that means before they fell into this potential well they could have been just about anywhere in the vicinity. Thus the fact they are currently in such a well strengthens rather than makes impossible the possibility that they could have been in a completely different orbit, namely colliding, in the distant past. What it DOES rule out is that they may collide in the future, since things fall into wells but don't spontaneously rise back out of them. (This paragraph rebuts somebody whose identity I forgot who used the resonance to claim collision in the past is thereby ruled out.)