The AstroDyke asks an interesting question: if NASA only has funds in the next Hubble servicing mission to repair either STIS or ACS, which should it be?
My vote should be obvious: I worked on STIS for 5 years. But it’s not just loyalty: Hubble lacks a good UV camera right now, and cannot take decent spectra at all in the optical or UV. ACS is a fantastic machine, but I think (I need to do more research, admittedly) that WF3 will cover a lot of the same ground sky.
So what do you think? Leave comments on her blog; give her some love.
April 27th, 2007 at 11:45 am
There is a lot of research on ring systems that can’t be done with WF3 that really need the ACS repaired. Dunno if that takes priority over the UV stuff, what’s your take?
April 27th, 2007 at 11:56 am
There’s basically no (working) UV spectrograph these days, and there aren’t any plans for any to go up. I think even though I used (and would use) ACS more, STIS is a more unique instrument, and like Richard says, WF3 will fulfill some of ACS’s capabilities (though, of course, because they were designed to work simultaneously, not all).
April 27th, 2007 at 12:14 pm
Absolutely, positively STIS. We can probe structure all we want, but without a decent UV spectrometer in orbit, we lack any serious tool to examine dynamics and physical conditions! Many, many elements have their primary electronic transitions in the UV, from where we get the best information about the temperature, density, chemical make-up, etc. of just about any astronomical object.
Admittedly, ACS has produced the hands-down best PR pictures in addition to some excellent science (e.g., getting down to the main sequence on distant stellar systems has been fantastic). But we really need a complement of instruments to do the best science we can as a whole field. We *need* a fully-working UV spectrometer in space.
April 27th, 2007 at 12:42 pm
Yeah, STIS. That’s somewhat colored by the practicality that it’s said to be more nearly impossible to fix ACS… But not only do we not have an optical or UV spectrograph in space now [1], but COS is essentially a 1-D device, sacrificing spatial resolution to increase throughput for high spectral resolution. QSO absorption and the IGM, here we come! However - STIS still reigns as the supreme black-hole hunter. Virtually all the solid measures of black-hole mass in other galaxies come from STIS, which is one reason why we’ve had the same sample for several years now. AO-fed spectrographs still don’t approach its resolution and lack of scattered light in the optical, which means it will be the only game in town for this and similar problems for a while yet. On top of all this, much of ACS’s survey capability will be served (albeit with not quite the field) by WFC3.
[1] Except FUSE, but it’s shorter-wavelength and a good complement to COS.
April 27th, 2007 at 1:11 pm
STIS. Even though I never used it and I have used ACS (and lost a project when it failed). A lot of ACS work can be done with WFC3, or even with AO from the ground, but STIS is unique, and JWST won’t have the UV capabilities of HST, so if it’s not done now it won’t be done in the foreseeable future.
Also, as mentioned above, it seems likely that ACS would need to be totally replaced rather than being repaired, which just isn’t on the cards.
April 27th, 2007 at 2:01 pm
Funny– of course, COS will do UV spectra! So STIS loses points for that (I should have mentioned that in the post) but STIS also has (or had) phenomenal spectral and spatial resolution. And it does spectra across the UV, optical, and near-IR.
I miss it sometimes. Every now and again I almost wish it were working so I could propose something on it (like RS Oph). Sigh. But then I remember how much work it was, and I’m glad someone else will do it… if they fix it. Sigh again.
April 27th, 2007 at 3:02 pm
Wasn’t hubble originally built so that the shuttle could retrieve it and bring it back to Earth? If so, why not bring it back down, upgrade everything, then relaunch it on a traditional rocket?
April 28th, 2007 at 2:31 am
is it seriously called an astro dyke? what were they thinking???
April 28th, 2007 at 6:26 pm
Dirty-g,
Astrodyke is the name of the blogger who asked the question. The instruments are called STIS and ACS in typical NASA acronym-ese.
Lab Lemming, yes, that was the original intent but had already been scrapped as pretty unfeasible at the time of launch in 1990. HST was not designed to be launched on a traditional rocket, so it would have had to go back up on a shuttle launch.
Ok, I’ll show my bias having worked on one of the original HST spectrographs (FOS), I’ll vote for STIS.
May 11th, 2007 at 8:34 pm
Thanks for the link, Phil.
Wow, NO votes for ACS over here yet. Veerrry interesting…