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From: eder@ssc-vax.UUCP (Dani Eder)
Newsgroups: net.space
Subject: Re: space telescope orbit
Message-ID: <298@ssc-vax.UUCP>
Date: Thu, 17-Oct-85 17:26:06 EDT
Article-I.D.: ssc-vax.298
Posted: Thu Oct 17 17:26:06 1985
Date-Received: Sat, 19-Oct-85 06:20:15 EDT
References: <8510161537.AA16848@s1-b.ARPA>
Organization: Boeing Aerospace Co., Seattle, WA
Lines: 29

> 
> I am confused as to how NASA is going to win with the
> space telescope's orbit:
> 
> If they orbit it at the same height as the shuttle, won't it drag the
> atmosphere and burn up like skylab in a few years?
> 
> And if they boost it to a higher orbit, how can anyone get to it to make
> repairs when it breaks?

     The Shuttle normally flies to 160 Nautical miles.  At that altitude
the payload capability is about 65,000 pounds.  In order to reach higher
altitudes, the Orbiter must carry more propellant, and hence less payload.
The Hubble Space Telescope is currently scheduled to be deployed at 320
Nautical miles (on 8 August 1986, flight 61-J).  The Orbiter Atlantis
is capable of carrying about 40,000 pounds to that height.  The Space
Telescope, including carrying cradle in the Orbiter cargo bay, weighs
27,700 pounds.

     As for drag, at 160 miles, drag lowers your orbit about 0.5 miles
per day.  At 320 miles, it is about 100 times less.  Over the 3 years
until the next scheduled Shuttle visit, the Telescope should fall about
5 miles.  The Telescope may be brought down at that time not because
the equipment has broken down, but because the incredibly thin layer
of aluminum on the mirror surface may evaporate off.  If not, they will
replace instruments, make any needed repairs, and drag it back up
five miles.  Then they will leave it in orbit for another three years.

Dani Eder/Boeing Aerospace/ssc-vax!eder