Spectrograph Expected to Reveal Images at Edge of Time

Scientists said they are starting work on a powerful device to be put in the Hubble Space Telescope in the 1990s that will record light images near the edge of time in the universe.

The imaging spectrograph funded by the National Aeronautics and Space Administration is expected to be up to 2,000 times more efficient than a similar device that will be part of the original space telescope system.

“We’ll be seeing objects as they were 14 billion years ago,” said J. Gethyn Timothy, a Stanford University research professor in applied physics who is working with a team of scientists at the Ball Aerospace Systems Division in Boulder, Colo.

“The universe is believed by many scientists to have started about 18 billion years ago, so we’ll be getting a view close to the edge of time as we know it,” he said. “Nearer objects, like the planets or closer stars, will be seen with tremendous clarity.”

‘Greatest Since Galileo’

Objects 100 million times more faint than can be seen with the naked eye will be recorded by the spectrograph through the space telescope.

“We are entering the greatest era in astrophysics since Galileo invented the telescope,” in 1609, Timothy said. “The image quality of the space telescope combined with the power of this spectrograph will change many of our ideas about space and time and the origins of the universe.”

The space telescope was to be launched in October on the space shuttle Atlantis, but it is uncertain how that schedule will be affected by the explosion of the shuttle Challenger and the resulting launch moratorium while the accident is investigated.

Scheduled for 1992-95

The two-year design phase of the spectrograph program is scheduled to start in July, but researchers already are beginning preparatory work, Timothy said. The device is to be inserted in the space telescope by shuttle astronauts sometime between 1992 and 1995.

A spectrograph breaks down ultraviolet and visible light radiation into a spectrum, enabling scientists to analyze the elements the telescope is seeing.

The spectrograph being planned now differs from similar devices in its sensitivity and its ability to record more precise images that can be converted into color photographs.

The new tool collects individual particles of light, called photons, maps them on one of four electronic panels, and times their arrival.

Electronic Detector

In the ultraviolet spectrum, the new spectrograph will use an electronic detector system invented by Timothy and Richard Bybee of Ball Aerospace.

Each photon hits the photosensitive surface of a gray plate about four inches in diameter into which millions of channels have been drilled. The photon is converted into an electron and then sent into one of the channels.

Two thousand volts of electricity are run across the plate, causing the electron to track down the channel, hitting the walls and producing more electrons.

“This avalanche continues down the channel, so from one photon in the front, you get a million electrons out the back,” Timothy said.

A grid of electrodes in the back collects the charge pulses and sends them through amplifier circuits to determine exactly where and when the photo arrived and enables scientists to fine-tune the image.

“We can identify very accurately the arrival time of the photons so we can do things like reconstruct the image and correct for spacecraft jitter,” Timothy said. “The pointing system will have some jitter, no matter how accurate a pointing system you build, and the space telescope’s will be the most accurate ever built.”