Re: A celestial tow job?

[John Mallinckrodt <ajmallinckro@CSUPOMONA.EDU>]

On Sun, 26 Dec 1999, Roger Freedman wrote:

> According to a NASA press release at
>
> http://spaceflight.nasa.gov/spacenews/reports/sts103/STS-103-13.html
>
> the shuttle released HST at 3:03 p.m. PST. At 3:39 p.m. CST Discovery
> fired its steering jets to change its orbit slightly, so that it would
> begin orbiting faster than the telescope and move away at just under 6
> statute miles per orbit. When we saw them, about three hours (i. e.,
> about two orbits) later, they would have been about 12 miles apart. The
> spacecraft altitude was about 400 miles, so the two objects would have
> been a bit less than 2 degrees apart in the sky --- which agrees pretty
> well with what we saw.

Hi Roger,

I looked up that press release after my post last night and did pretty
much the same calculation except, since the shuttle's elevation was only
about 30 degrees from Claremont, I figured its distance at closer to 800
miles. From my position the separation appeared to be a little less than
one finger's width at arm's length, similar to the diameter of the Sun or
Moon.  The press release also said that the shuttle had fired its steering
thrusters to put it in a slightly lower orbit so that the shuttle would be
ahead of the Hubble as I had speculated based purely on the relative
visual magnitudes.

> We also noticed someting else quite curious --- a narrow, faint band of
> luminosity extending along the orbital path of both Discovery and HST.
> This was about 2 degrees in length and about 2 or so degrees ahead of
> Discovery (i.e. to the east) in its orbit. I suspect that this was
> exhaust from Discovery's engine burn, which had fallen into an even
> lower (and hence faster) orbit due to interparticle collisions. What do
> you think?

I thought I saw something like that at first when it really did look like
the shuttle was towing something, but by the time both objects reached
their maximum elevation and brightness, I didn't notice it anymore.

Interestingly enough the heavens-above website seems to indicate that
Hubble will be *leading* the Shuttle during the two passes this evening
(the first of which is about half an hour from now at 5:15 local time,
probably still too light to see) by about 5 seconds or 25 miles (40 km for
the SI fanatic or the English impaired.)  Perhaps the shuttle moved up to
a higher orbit during the day?

John Mallinckrodt      mailto:ajm@csupomona.edu
Cal Poly Pomona          http://www.csupomona.edu/~ajm