Holland Ford's Team Gets Nod Over JPL, Goddard ----------------------------------------------------------------- By Emil Venere NASA has selected a team of scientists headed by Hopkins astronomer Holland Ford to design a new camera that may enable the Hubble Space Telescope to bring the very edge of the universe into focus. The Hubble Advanced Camera for Exploration will be eight times more sensitive than the present camera, promising to yield new insights into cosmology, while also providing important details about the solar system. It is scheduled to be installed by astronauts during a servicing mission in 1999. HACE will make the space telescope 16 times more efficient at finding galaxies and clusters of galaxies forming in the early universe, and it will give cosmologists a precise tool for probing the mysterious "dark matter." Astronomers plan to photograph the deepest possible reaches of space, surveying nearly a square degree of the sky--a region about the size of four full moons. The survey will take hundreds of hours of observing time. But when it is finished, scientists hope to see literally all the galaxies that emit optical light within that region, said Dr. Ford, a professor in the Department of Physics and Astronomy. "That's a very exciting possibility, the idea that we may be able to photograph an area of the sky and in those directions see virtually all of the galaxies in the universe," he said. The design was one of three proposals, facing stiff competition from the Jet Propulsion Laboratory and the Goddard Space Flight Center. JPL was considered a favorite, having designed both of the space telescope's previous cameras, Dr. Ford said. But his team had an advantage. Many of the scientists, himself included, were involved in the design of COSTAR, a device installed in December 1993 that corrected the blurred vision for three of the space telescope's instruments, impaired by a flaw in the primary mirror. "My own belief is that we have a very strong science team," said Dr. Ford, principal investigator for the HACE project, who has a dual appointment at Space Telescope Science Institute. Scientists and engineers developing HACE are from Hopkins, STScI, the University of Arizona, the University of California, Santa Cruz, and the University of Leiden in the Netherlands. Collectively, they've had "hundreds of years of experience" using the space telescope, which was launched in April 1990, said Jim Crocker, the HACE systems engineer. "They knew not only the science but they knew what the telescope was capable of," he said. "I think, for the first time, with this instrument we will be able to fully exploit the capabilities of the space telescope." Crocker conceived COSTAR's design while director of STScI's advanced programs office. He presently is on a one-year leave of absence at the European Southern Observatory, in Germany. HACE will be built by Ball Aerospace Corp., in Boulder, Colo., which also built COSTAR. The new camera's design includes a "solar blind channel" that blocks out all but certain ultraviolet light, enabling scientists to make detailed atmospheric studies of other planets in the solar system, said Paul Feldman, a Hopkins professor in the Department of Physics and Astronomy. HACE's superb sensitivity will enable much shorter exposures than those required by the present camera, called the Wide Field Planetary Camera-2. Long exposures of objects such as Jupiter cause smeared images of features in the Jovian atmosphere, since the planet rotates in the time it takes to capture the image. The new camera will snap pictures in 15 to 30 seconds, making much sharper images, said Dr. Feldman, a member of the science team. He wants to use HACE to study how solar radiation and solar winds interact with the upper atmosphere of Jupiter and other planets in the solar system. Another possible use will be to study the inner structure of comets. Because the space telescope is above Earth's image- distorting atmosphere, it is ideal for precisely measuring the distances of galaxies. By carefully measuring the way that light from a distant galaxy fluctuates, astronomers can calculate precisely how far away it is. WFPC-2 isn't efficient enough to make the measurements for a large sample of distant galaxies--it takes too much observing time to collect enough light. A large sample is needed in order to map the large-scale distribution of matter. The new camera's increased efficiency will make those measurements possible, said Marc Postman, an astrophysicist at STScI. HACE will feature a novel design that has the fewest possible number of reflecting surfaces, so that fewer photons are lost. Other advanced features making the camera more efficient include highly reflective coatings and a larger and more sensitive imaging chip, made up of imaging sensors called charge-coupled devices. The CCDs will form an array containing 4,096-by-4,096 pixels, compared with the current camera's 1,600-by-1,600 pixels. The new camera won't actually replace WFPC-2, which was installed with COSTAR in 1993. HACE is an axial instrument, meaning it is located perpendicular to the focal plane. It will replace one of HST's four axial instruments, depending on which one is least needed by the time of the servicing mission, Crocker said. WFPC-2 is a radial instrument, the only such instrument on HST, and is located parallel to the focal plane. George Hartig, an astrophysicist at STScI, is project scientist for HACE. One other Hopkins scientist, postdoctoral fellow Tom Broadhurst, is working on the project.
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