Located on the Johns Hopkins University's Homewood Campus in Baltimore, Maryland, the Space Telescope Science Institute (STScI) is a research center operated by the non-profit organization Association of Universities for Research in Astronomy (AURA) for NASA. STScI's primary mission is to design, operate, and maintain the ground systems necessary for the science and engineering operations of the Hubble Space Telescope.

Contrary to popular belief (or at least, the belief popular among the extremely small number of people who have actually heard of STScI), the Hubble is not really controlled from the institute. STScI is responsible for all of the preprocessing necessary to use the telescope for scientific observations, and analyzes the data that results from said observations, but the actual data transmission and various housekeeping and commanding activities are relayed to the Hubble from NASA's Goddard Space Flight Center in Greenbelt, Maryland.

Without getting too terribly esoteric, using cryptic acronyms, or divulging any sensitive information, here is a general outline of STScI's role in managing the use of the Hubble:

1. An astronomer or other observer wishes to use the Hubble to look at something. They submit a proposal to STScI, which gives details about the desired targets (i.e. the celestial bodies they want to point the Hubble at) and the types of observations (called exposures) they want to make using specific scientific instruments onboard the Hubble.
2. STScI runs the proposal through a preprocessing system that parses it to make sure it is syntactically correct.
3. The output from the preprocessor is run through a planning system that checks if the proposed exposures are feasible. There are a mammoth number of constraints, many quite complicated, on the telescope's operations: some instruments cannot be operated simultaneously with other instruments, there are timing issues with the Hubble's orbit, and so on.
4. The output from the planning system is sent to several downstream schedulers that take care of all the nitty gritty details of scheduling the observations in the most efficient, cost-effective way possible. The Hubble costs an enormous amount of money to operate, and obviously, NASA wants to get some bang for the taxpayers' buck. The scheduling systems ensure that the Hubble's instruments are always doing as much work as possible at any given moment.
5. STScI sends the master observing plan to Goddard, where it is merged with the plan for housekeeping activities, translated into commands that the Hubble's onboard computer can understand, and then sent to a ground station in White Sands, New Mexico that uplinks to the Hubble itself through the Tracking Data Relay Satellite.
6. When the Hubble completes the observations, it sends the raw data from science and engineering operations back to Earth through the same satellite. Some of the data is available in real time so that the astronomer can go to a special workstation and see the telescope in action on their proposal. The rest of the data is collected at Goddard and then sent back to STScI.
7. STScI is responsible for all data analysis, and for ensuring that the data makes its way back to the astronomer who originally submitted the proposal. If any of the exposures are particularly interesting or visually stunning, they are sent to an artist who colors them in before they are posted on the web site and printed on posters, mugs, t-shirts, and various other paraphernalia to be given out as souvenirs to STScI and NASA visitors.

When dealing with systems of this scale, code maintenance assumes utmost importance, as miniscule unforeseen glitches can have potentially disastrous effects. Thus, more than half of STScI's manpower is devoted to maintenance. The rest work on developing new and improved ground systems. Keeping the systems in a constant state of evolution behooves STScI because the Hubble is a long-range mission (the current plan is to keep it in operation until 2010), so making the systems more efficient and more easily maintainable has a quantifiable payoff for the institute.

STScI will be performing similar duties for the Hubble's successor, the James Webb Space Telescope (formerly known as the Next Generation Space Telescope).

Useful facts for visitors to STScI:

• The institute isn't a tourist attraction, and it doesn't readily accommodate people just popping in and asking for a tour. To visit, attend one of the public lecture series, or call ahead and make arrangements (details are available on their web site).
• The question most frequently asked by visitors is: "Can I look through the telescope?" No, you may not. The Hubble is not sitting in the institute's backyard. It floats 600 kilometers above the Earth's surface, completing an orbit of the globe every 95 minutes. Using it is much more complicated than simply sticking your peeper up to an eyepiece.
• STScI is also home to the Hubble Cafe, one of the best cafeterias in Baltimore. You can find it on the first floor of the Muller building on San Martin Drive. In addition to offering reasonably priced, scrumptious food (as cafeterias go, that is), this eatery provides a social focal point for employees.
• The institute has a room filled with souvenirs for visitors. If you aren't offered one, ask. Some of them are not free (for instance, Hubble-related apparel will cost you), but there are lots of free posters and such with some spectacular shots from the telescope.

To learn more about STScI:
http://www.stsci.edu

To see pretty pictures from the Hubble:
http://hubblesite.org