Re: Hubble Servicing

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Comments:
> > > I'm a bit puzzled about the entire Hubble servicing philosophy. Since > > > the on-orbit repair and replacements seem to be rather difficult (with > > > huge amounts of pre-flight training), why don't we simply de-orbit the > > > Hubble in the cargo bay and reboost it on the next mission. > > Of course you still would need pre-flight training for this, so that > > cost would only be slightly diminished if at all. Remember you > > would have to train on stowing the HST, which I could imagine would > > be very difficult and would require lots of training. > > > I'm sure > > > some would say that that takes two flights where one would do, but it > > > seems that we could schedule the pickup missions with on board science > > > and/or satellites that could be released near Hubbles orbit. > > Remember that every item you put on the Shuttle makes it all the more > > heavier. This will limit how high the Shuttle can go (and you > > want it to go very high). Also, any additional satellites would > > lengthen the mission (as they would need to devote time to releasing > > them). There are limits to the fuel (both Shuttle and human) aboard > > also. If the method you suggest was followed, the Shuttle would be > > devoted only to the retrieving of the HST. > > > I do realize that many birds have very specific orbital requirements > > > so there would be delicacy in scheduling. Overall, this would allow full > > > refurbishment of systems in an environment much easier to do repair > > > and replacement of components-on the earth. > > > I'm sure NASA has kept all > > > the packaging components necessary for the reorbit of the Hubble. I'm > > > also sure to retrieve the Hubble in the cargo bay would probably > > > require a space walk, but again, this seems much easier than the > > > complicated on-orbit repair missions. Can someone enlighten me? > > > > > > > > It's complicated either way. The "bringing down HST to Earth" method > > would loss many months of scientific observations (maybe even years > > if the Shuttles have lengthy delays) and would probably cost more > > (possibly substantially more) than the current on-orbit servicing missions. > > Scott > Thanks Scott for the reply. My assumption was that NASA has studied this option heavily but rejected it for the current scenario for some good reasons. The telescope being off line for months makes the most sense as a reason not to do this but it seems that good scheduling could minimize this. As soon as the Hubble was repaired, another orbiter would be prepped to take it back up. I realize that due to weight limitations that NASA couldn't take other science on the mission to re-orbit the Hubble (consider this the same as the repair mission), but the mission to retrieve the Hubble should be relatively empty (with the exception of the carriage for the Hubble) and this payload volume and weight could be used for other science or payloads. At least that is my thinking! One of my additional concerns was that de-orbiting and re-boosting the Hubble is vibrationally hard on the telescope and carries some finite but non-negligable risk of loss (eg, the Challenger). There may well be other reasons of which I've only scratched the surface, but thanks very much for the discussion. As always, with real science and engineering projects, reality is much more complicated than the casual observer realizes. At any rate, Congratulations to the crew and ground staff on a job well done in returning the bird to service and for all the hard work on the web site answering questions and comments such as mine. This really makes us feel we are getting our tax dollars worth. > Regards, > Brian

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