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Launch Series: SIRTF Mission Overview
Question and Answer Board

Andrew from Knoxville, Maryland
What kind of telescope is going to be sent into space with this infrared technology? Is it similar to the Hubble?
Well Andrew the telescope is similar to the Hubble in that it has a primary mirror, a secondary mirror, and an instrument suite behind the primary mirror to which the beam is directed. The main differences from the Hubble are firstly it is made of beryllium rather than glass, which the Hubble is made of. Secondly, it's cooled through the cryogenic system that you've heard about to a temperature of about one and a half degrees Calvin. And the third difference is it's only about a tenth of the area or a third of the diameter of the Hubble, but we expect to achieve scientific results as exciting as those achieved by the Hubble because we are exploring a different part of the electromagnetic spectrum.
Jenny from Las Vegas
How far will SIRTF be positioned from Earth?
Well Jenny, SIRTF will not be positioned at a particular location relative to the Earth; it will drift away from the Earth at a distance of at about a tenth of an astronomical unit per year. That's about one tenth of the distance from the Earth to the Sun. So you can imagine as I said in my earlier clip, SIRTF following the Earth around the Sun like a faithful puppy dog, but lagging behind it by about a tenth of an astronomical unit per year. At the end of our mission we will be about a half or six tenths of an astronomical unit from the Earth.

Host: What size is this observatory?

That is a very good question Tiffany; the telescope is about 85 centimeters in diameter. The whole observatory with the telescope, the instruments, and the spacecraft is about 15 feet tall and weighs about a ton.
Kristin from Mooresville
How long will SIRTF be in space?
Well SIRTF will be in space for a real long time, essentially it will be in space forever, but we will only be using it for our prime cryogenic mission for two and a half to perhaps six years depending on exactly how well the cooling system performs. Following that we might operate for several more years as a mission using only our shortest wavelength detectors because when we're out there in space once we run out of cryogen, it's still real cold and we'll still be able to do interesting science with parts of the instrument package. But following the cryogen exhaustion, SIRTF will continue to orbit the Sun that you can think about it as sort of a small asteroid in a peculiar orbit.

Host: What would you say that you actually turn on, on SIRTF sort of, when you start trying to get data from it?

Well it's kind of a staggered or graduated process because the telescope cools down and the full scientific payload can't be exercised until the telescope reaches its operating temperature about 45 days after launch. So about 35 days after launch we'll complete the focusing of the telescope. About 60 days after launch we'll have completed the validation or check out of the function element of the observatory. And then the following month, the third month of the mission will be devoted to tuning up the scientific measurement modes and so fourth. We hope to release the first science data at a press conference in mid-December.
Richard from Safety Harbor
How will the data be processed and output? How soon will it be available to the public?
Well Richard, the data will be down-linked from the spacecraft twice per day through the capabilities of the deep space network. And those raw data frames, if you like, will be sent to the SIRTF science center on the Caltech campus, which will process them using specialized data processing pipelines. The data will start becoming available to the public with the press conference that I mentioned at about mid-December and following that we expect to have a continuous stream of data products available to the public through the SIRTF science center website. And the URL for that I should say is And if you were to go over there now, or after you finish watching this video, you'll find a lot of interesting information about the SIRTF mission, a personality profile, educational activities, and lots of good scientific information on which I'm sure you would enjoy looking at.
Geoff from Buies Creek
What will SIRTF detect?
Well Geoff, we are expecting it to detect objects from the outer regions of our Solar System in the so-called Kuiper belt objects orbiting beyond Neptune through regions in the local universe where stars are forming, looking at brown dwarfs, cold objects which have never quite made it to stars but are still visible in the infrared because their heat is diffusing our way. Then beyond our galaxy we will be looking at distant galaxies that are in the throws of active bursts of star formation, galaxies that are powered by accretion on the black holes. And at the earliest and most distant galaxies that we can see maybe a few burning years after the origin of the universe and the big bang. Now those are the things that we know we can see, but equally exciting as Dave was saying earlier, is the fact that SIRTF's measurement capabilities are so powerful compared to what's been available in the past. And we have every expectation of making new discoveries, so the things that we’re going to see that are going to be the most interesting from many points of view I can't describe for you yet.
Juan Rodriguez from Gijon (Spain)
The Universe has been studied by some infrared space observatories, like ISO or IRAS...Are you expecting any special discovery with SIRTF?
Well let me take a second Juan to explain about ISO and IRAS. IRAS was the pioneering infrared space observatory. It was a joint US, UK, and Netherlands project, which flew in 1983 and surveyed the entire sky in the infrared. It also demonstrated many of the technologies that were used on the subsequent observatories. ISO, the Infrared Space Observatory, was a project of the European Space Agency operated from about 1993 to 1996 or 1995 to 1998; I've forgotten the details. It was a very good mission; it had a flexible instrument package like SIRTF does. It followed up on many of the results from IRAS and had lots of exciting scientific results for the European and the US communities. And these two observatories together set the stage for SIRTF. SIRTF goes beyond either by using the powerful infrared detector rays that I talked about earlier. So we're definitely expecting to build on their discoveries, but to go beyond we’re looking further into space with higher sensitivity and making new discoveries with the type I just talked about. So it’s an evolution and beyond where SIRTF leaves off future missions will take on in the coming years.

Host: Mike I mentioned earlier in your intro, 26 years on this project this is probably like your baby. How are you feeling now, I mean we're days away from launching?

My feelings I would say are a combination of pride and anticipation. I'm proud of the work that we've done as a group and that Dave and I have directed to work as a team of scientists, engineers, and managers with the support of Headquarters to build a really beautiful instrument. It's beautiful to look at and it's beautiful in terms of what it can do. So that is very satisfying, but of course I am really anticipating now the excitement and the satisfaction of seeing the scientific results start to come back and I should have said in answer to your earlier question, we’ll know within a few weeks that we're good to go for the science program, which I talked about. It will just take a few months to get things tuned up so that we can start producing useful scientific data.
Carl from Portland
Is the SIRTF aimed at the earth or into the vast darkness of space and other planets?
Well Carl, we can't really look at the Earth with SIRTF because the Earth is too bright. So we'll be looking mainly outward starting with objects in our own solar system like Kuiper belt objects, comets, and so fourth; and then beyond that into the galaxy and beyond.
Carlos from Mexico City
Will the new telescope aid in the quest to uncover black holes?
Well we will definitely be looking at objects that are powered by black holes. A black hole of course is a dense region in space from which nothing can escape. But you can study black holes by seeing their influence on material that is very close to them, in what's called an accretion disk. Accretion disks will have a signature in the infrared that may allow us to infer their properties even though they might be in a region where there's a lot of dust and gas that can't be probed as effectively at visible or ultra violet wave lengths. So we’ll definitely be on the track of black holes and understand how their properties and abundance so to speak vary with cosmic time.
Debbie from Melbourne
How will the data obtained be used with the data already coming from Hubble and Chandra?
Well Debbie, these three observatories probe different regions of the electromagnetic specter, and that's different regimes or different physical processes. There is an awful lot of synergism between Hubble, Chandra, and SIRTF and perhaps the best way to describe it is to say we'll be doing our deepest surveys, our most penetrating looks back into space and time, in the same regions in space, which have also been studied by Hubble and by Chandra. So we'll have a kind of panchromatic or broad view of say the properties of distant galaxies, where Chandra looks primarily at the hottest gas and most uniquely at the regions powered by black holes. SIRTF might look at hidden star formation and at the star formation, the properties of the stars, which formed over the lifetime of the galaxy. And the Hubble might be looking at current, ongoing star formation and massive young stars and it's sort of the morphology in a way that's not possible with SIRTF. There will be a tremendous amount of synergism and it's exciting to be joining our sister great observatories.
Bill C. from York, Maine
How will we benefit from this upcoming launch?
Well Bill, that's a very insightful and legitimate question because after all you're helping to pay for this. And I think there are a number of ways, but I think perhaps the best answer is to say that SIRTF is another step in man's ongoing quest to understand the universe around us. We all benefit from the insights, the understanding, and the marvels that NASA's space program returns to us. They illuminate our life on a daily basis and give us a better understanding of the universe that we live in. In addition, the technology that's been developed for SIRTF has applications in daily life in things ranging from fire fighting, from thermal engineering, and also even in quality control for semi-conductor chip fabrication. And finally, SIRTF is a training ground on the one hand for future scientists and engineers, but on the other hand astronomy is a very accessible science and SIRTF will help inspire future generations of students and help them serve as a good tool for enhancing their understanding of science even if they are going into other careers, which is extremely important. It is very important for all of us that we have a scientific, literate and aware public and SIRTF will be a step towards achieving that. So there are benefits to scientists, there are benefits to the general public, there are benefits in specific industrial applications, and there are benefits to mankind.