A BIG STEP BACKWARD

The art and reality of building a major orbiting observatory has been compared to the creation of one of Europe's great cathedrals. Both require a grand plan, an ability to keep working under stress and similar amounts of toil.

The competition to build the James Webb Space Telescope ended last year with the selection of a contracting team headed by Northrop Grumman Space Technology. Eight years from now, an Ariane 5 is expected to boost the 5,400-kg. (11,880-lb.) observatory toward the second Lagrangian point (L2), 1.5 million km. (930,000 mi.) beyond Earth's orbit. There, the Sun and Earth will be on a relatively straight line with the satellite, which minimizes the effects of their light on its optics, and their gravitational pull will be pretty much in balance, giving it a relatively benign parking spot.

L2 OFFERS THE closest practical orbit for the deep space cold soak that the telescope needs. To assure a temperature range of 30-35K, the telescope and its Integrated Science Instrument Module (ISIM) will be shielded from sunlight by a five-layer sunshield as big as two tennis courts. In this cold, its infrared detectors will be so sensitive that they can chase the red-shifted light of receding time as far back as the start of time itself, back some 14 billion years to the moment when astronomers think the Big Bang went bang.

Astronomers call these first moments of creation the "dark ages" because no observatory has been powerful enough to penetrate them. What scientists know about the opening scenes of time is theory; they haven't seen the enactment.