?

Log in

Bram Sci

Hubble Not Buried Yet!

Hubble Not Buried Yet!

Previous Entry Share Next Entry
galafractaxyl
Links: NY Times, NASA, NASA TV

The Shuttle will fix Hubble in May 2008, extending its life to 2013, if all goes well, the NASA administrator Michael Griffin has decided. After the Shuttle Columbia disintegrated in 2003, NASA planned to send Shuttle missions only to the International Space Station, which needed to be completed, and from which the Shuttle could be inspected for repair. A robotic mission to fix the Hubble without human assistance was proposed but deemed infeasible.

The new instruments to be placed aboard HST--otherwise they'd languish on the ground, as they are already prepared--are COS, the Cosmic Origins Spectrograph, and WFC 3, the 3rd version of the Wide Field [Planetary] Camera (used to be pronounced Wiff-Pick--when did they drop the P?).

Links to these new instruments:

COS, WFC3

Goddard Space Flight Center page on WFC3

COS mini-handbook, WFC3 handbook

Summary:

COS provides spectra in the 1150 to 3200 Angstrom range (UV light that doesn't get down through Earth's atmosphere) with higher sensitivity for faint objects than ever before

How does it compare to STIS, the Space Telescope Imaging Spectrograph, that's currently on board? Well, it doesn't go to such high resolution but it has higher sensitivity. This is from the "mini-handbook" linked above:



This is a complicated table--how do I read it? Well, FUV is Far UV--I like to observe in the FUV! lambda/delta lambda is the resolution. I like to work with a resolution of 20,000 to see Doppler shifts of 15 km/s or so, which are important in the star systems I study. (A stellar wind is about 1,000-3000 km/s and X-ray binaries usually orbit with 100-500 km/s... an accretion disk spins at about 300 km/s at the edge).

If I used the COS G130M (the G130M is a configuration choice, probably having to do with gratings, etc.) near 1300 A, the sensitivity Slambda would be 1.0.
If I used the STIS E140M and added up each 2.3 wavelength bins, the sensitivity would be only 0.14! That's only 1/7th as sensitive! (I know that by heart b/c they used to say Pi was about 3 1/7.) But if I opted for 2 times lower resolution (R=10,000) with the STIS G140M, I'd still have only 0.66 of the sensitivity, compared with 2.0 for the COS binned by 2 to get the same resolution of 10,000. So either way it looks like COS should be better--if everything works!

WFC3 provides wide field images and spectra from the UV through the IR and compares favorably with older instruments:



I don't think that the upcoming deadline for proposals to use HST includes the chance to use these new instruments... I think that will be for next year... and future years!
Powered by LiveJournal.com