Faint Object Camera

Faint Object Camera. The Faint Object Camera (FOC) was a sophisticated astronomical instrument and one of the five original axial scientific instruments aboard the Hubble Space Telescope. Developed and provided by the European Space Agency as its major contribution to the Hubble program, it was the last of the original instruments to use a photomultiplier-based detector system. Designed to achieve extremely high spatial resolution, it was the premier instrument on Hubble for observations of very faint targets in the ultraviolet and visible light spectra, operating for over a decade before being replaced during a Space Shuttle servicing mission.

Overview

The FOC was conceived to exploit the unique potential of the Hubble Space Telescope's unobstructed view above the Earth's atmosphere. Its primary scientific goal was to conduct deep imaging and spectroscopy of astronomical objects with very low surface brightness, a task impossible for ground-based observatories due to atmospheric seeing. As part of the international collaboration between NASA and the European Space Agency, the FOC was built by a consortium led by Dornier Flugzeugwerke in Germany, with scientific leadership from the Space Telescope Science Institute in Baltimore. It functioned as a highly specialized camera capable of discerning fine details in the light from distant quasars, the cores of active galaxies, and faint structures around bright objects.

Design and capabilities

The instrument's design centered on a complex optical system that used a series of mirrors to magnify images before they reached its detectors, minimizing the degradation of signal-to-noise ratio. It employed two independent detector chains: the F/48 relay for high-resolution imaging and the F/96 relay for faint, extended objects, each utilizing image intensifier tubes and photomultipliers to scan the target. This design allowed it to operate across a broad wavelength range from the far-ultraviolet at 115 nm to the red end of the visible spectrum at 650 nm. Key capabilities included polarimetry and the use of various filters and coronagraphic masks to block out the glare from bright stars, enabling the study of nearby protoplanetary disks and faint companion stars.

Scientific contributions

The FOC made numerous landmark observations that significantly advanced astrophysics. It provided unprecedented views of the energetic jets emanating from the core of the elliptical galaxy Messier 87, offering clues about supermassive black holes. The camera was instrumental in confirming the existence of protoplanetary disks around young stars like Beta Pictoris, directly imaging the structures where planets form. It obtained deep images of the Hubble Deep Field, helping to constrain the evolution of galaxies in the early universe. Furthermore, it studied the atmosphere of Saturn's moon Titan, observed the aftermath of the Comet Shoemaker–Levy 9 impact on Jupiter, and took detailed measurements of Cepheid variable stars in distant galaxies, refining the Hubble Constant.

Operation and mission history

Launched aboard the Space Shuttle Discovery during mission STS-31 in April 1990, the FOC began operations shortly after Hubble's deployment. Its initial performance was hampered by the telescope's spherical aberration in its primary mirror, a flaw discovered in June 1990. Despite this, the FOC's unique design allowed it to be less affected than other instruments, and it still returned valuable scientific data. The corrective optics installed during the first servicing mission, STS-61 in 1993, which included the Corrective Optics Space Telescope Axial Replacement, fully restored its intended capabilities. The FOC continued to operate successfully for nearly nine more years, outlasting several other original instruments.

Legacy and decommissioning

The FOC's final observations were taken in January 2002. It was removed from the Hubble Space Telescope during Servicing Mission 3B (STS-109) in March 2002 and replaced by the more advanced Advanced Camera for Surveys. The decommissioned instrument was returned to Earth and is now part of the permanent collection of the Deutsches Museum in Munich. Its legacy endures in the vast archive of data it produced, which continues to be used by researchers worldwide. The technological experience gained from the FOC directly informed the design of later Hubble instruments and contributed to the planning for future space observatories like the James Webb Space Telescope.

Category:Hubble Space Telescope instruments Category:European Space Agency Category:Space cameras