Hubble finally has the stars in its eyes.

Hubble finally has the stars in its eyes

"First light" -- the Hubble Space Telescope's first look into space -- elated scientists and engineers who had worked so long to ready and orbit the $2 billion craft. "Our image quality is significantly better than we were concerned that it might be," says James Westphal of the California Institute of Technology in Pasadena.

On May 20, ground controllers at NASA's Goddard Space Flight Center in Greenbelt, Md., commanded Hubble to take two photos of the same area, one exposed for 1 second and the other for half a minute. The subject of the telescope's first photographs was part of an open star cluster known as NGC 3532 in the southern-sky constellation Carina, or the Ship's Keel. Enhancement of the first photo later revealed that what had appeared as a single, diffuse bright spot was actually two stars (shown at right), although it remained unclear whether the two orbited each other as a binary system.

For comparison, the left image depicts the same region as it was photographed from the ground by Eric Persson of the Las Campanas Observatory in Chile, using the 100-inch DuPont reflector telescope. This image was made through a visible-light filter equivalent to the one on the space telescope, using the same kind of charge-coupled device to detect the star cluster's light. The angular resolution or sharpness of the pictures is 1.1 arc-seconds. The space-based image has a resolution of about 0.2 arc-second.

Since Hubble's April 25 release from the space shuttle, engineers have labored to improve the instrument's focus by adjusting its mirrors. Westphal, chief scientist of the wide-field/planetary camera that captured Hubble's first light, says the adjustments should approximately double the sharpness of its pictures. Engineers also want to reduce several wobbles and aiming uncertainties that limit the telecope's aiming accuracy. Along with better focusing, improved stabilization should help sharpen photos that require the telescope to hold steady for extended periods.

Still awaiting their first light from the stars are the telescope's other scientific instruments (SN: 1/6/90, p.8). These include two spectrometers that measure light to see what it shows about the composition and temperature of its source; a camera designed to look specifically at faint objects by counting individual photons of light; and a high-speed photometer to measure brightness changes as brief as 20 millionths of a second in objects such as pulsars. Also part of the research equipment is the telescope's guidance system, which will measure subtle motions such as those of stars that may be wobbling because they have planets orbiting around them. The telescope should begin its actual scientific studies in about three to six months.