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Herschel telescope ready to shift science into high gear

Posted: January 2, 2010

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The Herschel telescope's highest resolution instrument will begin observing the infrared universe this month after operations were suspended in August due to faulty electronics, according to the mission's project scientist.

Artist's concept of the Herschel spacecraft. Credit: ESA
The Heterodyne Instrument for the Far Infrared was built to obtain revolutionary new information on dynamic star-forming regions, galactic nuclei and interstellar gas. HIFI will study the motion and composition of material throughout the universe, specifically hunting for water and carbon by observing a single pixel in the sky at a time.

Before HIFI could study its first scientific target, the instrument was crippled by a momentary glitch that triggered a chain of events leading to the permanent failure of a diode inside the Local Oscillator Control Unit, or LCU.

A single event upset Aug. 3 activated an automatic switch off to protect components from a power interruption, but the spacecraft was still providing electricty to the instrument. This caused a voltage spike in a power converter, damaging the diode, according to engineers.

The spectrometer had already made early observations during a performance verification campaign this summer, but the August glitch occurred before HIFI began formal scientific work.

The LCU controls an artifical signal created inside HIFI that mixes with the far infrared light from the universe, creating a signal that is easier to detect and process. The ingenious observing technique allows astronomers and astrophysicists to study hard-to-see objects and regions throughout the universe.

HIFI carries a duplicate set of electronics that was turned on in early December. The instrument itself will restart observations around Jan. 10, according to Goran Pilbratt, Herschel's project scientist at the European Space Agency.

"The redundant set of warm electronics units were turned on and worked correctly and exactly as expected," Pilratt said. "As you can imagine, we are all immensely excited to finally get HIFI going again."

When HIFI is restored, scientists plan to quickly test the instrument and give HIFI up to half of Herschel's observing time between February and April.

Managed by the Netherlands Institute for Space Research, HIFI promises to glimpse inside the chaotic centers of galaxies and deliver data shedding light on the birth and evolution of stars and planetary systems throughout the galaxy. Closer to home, HIFI will also measure the chemical make-up of planets and comets in our solar system.

The $1.3 billion Herschel observatory was launched May 14 in tandem with Planck, another European telescope designed to seek out the relic light from the Big Bang.

Herschel captured this image of a star-forming region 1,000 light years away in the constellation Aquila. About 700 forming stars are inside this complex of dust and gas, which is located in a mysterious ring of stars called Gould's Belt. Credit: ESA and the SPIRE and PACS consortia, P. André (CEA Saclay) for the Gould's Belt Key Programme Consortia
Herschel operates in an orbit around the L2 libration point, a location about 1.5 million kilometers from the night side of Earth, where gravity from the planet and the sun balance to create a stable location for spacecraft studying the cosmos.

Most of Herschel's work is now in routine operations, and the observatory's other two instruments have already collected a scientific bounty of stunningly artistic views of the universe.

Herschel's infrared sensors are cooled by cryogenic liquid helium, allowing the telescope to see faint and distant objects hidden behind dust clouds opaque to the human eye. The spacecraft's coldest detector is chilled to 0.3 Kelvin, or below -459 degrees Fahrenheit.

The telescope will continue operating until the helium runs out in early 2013.

Herschel views the universe through an 11.5-foot-wide primary mirror, the largest telescope ever flown in space.

The observatory's other two instruments are the Photodetector Array Camera and Spectrometer and the Spectral and Photometric Imaging Receiver, respectively called PACS and SPIRE. They are capable of capturing and analyzing images in a wide swath of the electromagnetic spectrum, ranging from infrared to submillimeter wavelengths.

Herschel is the first space telescope to see light in submillimeter wavelengths, which are sandwiched between infrared light and radio waves on the electromagnetic spectrum.

PACS and SPIRE cover different sections of the spectrum, and scientists combine data from both instruments to produce a single image.

"The other two instruments have produced absolutely fantastic initial science, and we now want HIFI to show what it can do," Pilbratt said.

More than 30 science teams presented initial results from Herschel's demonstration observations at a conference in mid-December. The sentiment at the workshop was that Herschel is meeting or surpassing expectations, according to Pilbratt.

This five-color composite image was captured in September, showing filament-like structures of cold gas thousands of light years away in the constellation of the Southern Cross. Scientists did not expect this level of activity in such a dark, cool region of the sky. Credit: ESA and the SPIRE and PACS consortia

A team of scientists has already begun using Herschel to look for distant galaxies from the earliest history of the universe. The project is still in its preliminary stages, but researchers from six countries have already used Herschel to observe more than 27,000 galaxies.

"The submillimeter sky is absolutely paved with galaxies," said Jason Glenn, a SPIRE co-investigator from the University of Colorado at Boulder.

Glenn said the Herschel Multi-tiered Extragalactic Survey expects to detect hundreds of thousands of infant galaxies more than 10 billion years old, in the first quarter of the universe's life.

Another group is surveying sections of the sky in submillimeter and far infrared light, looking for undetected nearby galaxies, dark matter, blazars and galactic dust. Herschel has already started the observations and detected thousands of sources, ranging from supermassive black holes to infant stars.

The Herschel submillimeter survey found 15,000 light sources in 16 hours of observations. A ground-based survey over 20 nights only discovered five sources in 1998.

Scientists have also pointed Herschel toward Mars, Neptune and a comet in the first phase of a project to study the distribution and behavior of water and other volatile minerals in the solar system.

Herschel has also already peered deep inside the Milky Way's star-making nurseries, clouds of dust housing protostars and dark globules, which are believed to be among the coldest objects in the universe.