April 17, 2003. Copyright 2003. Graphic News. All rights reserved.

GN15071 -- Picture caption: Technicians at Ball Aerospace prepare the 85-cm (33.5-inch) primary mirror for the SIRTF cryogenic telescope. The mirror is fabricated with light-weight beryllium. MUST CREDIT Ball Aerospace & Technologies Corp.

Telescope to peer back through space and time

LONDON, April 17, Graphic News: NASAÕs first mission following the tragic loss of the shuttle Columbia is the launch of a powerful space telescope that will open a new window to the universe.

The $1.2 billion (1.1 billion euros) Space Infrared Telescope Facility will study extremely distant objects visible only in infrared light. Trailing the EarthÕs orbit around the Sun like a puppy dog and chilled to a few degrees above absolute zero, the compact 850-kilogram (30,000-lb) observatory can detect heat as faint as the pulse from a TV remote control 16,000 kilometres (10,000 miles) away.

Known by the dry acronym SIRTF (pronounced ÒSIR-tiffÓ), the instrument completes NASAÕs suite of four Great Observatories to study different parts of the electromagnetic spectrum: its visible-light cousin, the Hubble Space Telescope; the Chandra X-ray Observatory; and the Compton Gamma Ray Observatory.

Infrared detectors can see longer wavelengths than the red light visible to our eyes. As the universe expands, starlight from distant galaxies is shifted from blue to red and, ultimately, into the infrared. Most radiation emitted from galaxies as they coalesced in the aftermath of the Big Bang -- some 13.7 billion years ago -- now lies in the infrared. SIRTF will enable scientists to look farther back in space and time than was previously possible and watch stars and planetary systems in the making -- targets that until now have been shrouded in dusty mystery.

ÒWith this mission, we will see the universe as it was billions of years ago, helping us pinpoint how and when the first objects formed, as well as their composition,Ó said Dr. Anne Kinney, director of the astronomy and physics division at NASA Headquarters in Washington, D.C.

During its life, SIRTF will also probe the chemical composition of enigmatic brown dwarfs, Òfailed starsÓ that lack enough mass to trigger nuclear ignition. Some scientists think brown dwarfs may account for some or all of the elusive Òdark matterÓ thought to be prevalent in the universe. The mission will also study planets in our own solar system, asteroids and comets. 

The observatoryÕs 85-centimetre (33.5-inch) telescope will feed traces of heat to three science instruments. The infrared array is a general-purpose camera for near-infrared to mid-infrared wavelengths. The infrared spectrograph breaks light into its various wavelengths, much like a prism, to help astronomers study the composition of stars and planets. The multi-band imaging photometer will gather pictures and spectroscopic data at far-infrared wavelengths to study cool, dusty objects.

To detect these primitive heat traces the instruments have to be extremely cold -- as cold as absolute zero, or minus 273 degrees C (minus 459 degrees F). A combination sunshade/solar panel will do part of the job, and 340 litres (90 gallons) of liquid helium coolant the rest. The instruments are contained in a Dewar -- a giant vacuum flask through which the helium coolant, or cryogen, circulates.

Sensitive observatories such as SIRTF and the Hubble Space Telescope must avoid looking at -- or anywhere near -- extremely bright objects such as the Sun, Earth, and Moon. This means that the telescope must point away from the Sun to reduce heating by solar radiation, but it must not point too far away because of the need to illuminate its solar panels and produce electricity to power the observatory.

Data will be stored in an eight-gigabit, solid-state memory, equivalent to more than 12 music CDs, and ÒdumpedÓ back to Earth once or twice a day.

The 4.3-metre-long (14-feet-long) craft will be boosted into space atop a Boeing Delta 2 rocket from Cape Canaveral. If all goes well, over its five-year life it will beam back a staggering 100,000 observations -- a scientific windfall to astronomers who have been waiting since the project got under way in 1983.
/ENDS

Sources: NASA, Jet Propulsion Laboratory