HST Booklet

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January 7,  2021

Hubble Space Telescope Booklet - Winter 2021

Observatory brochure including instrument pocket guides with detailed characteristics.

3 MB

Advanced Camera for Surveys (ACS)

The ACS is a camera designed to provide HST with a deep, wide-field survey capability from the visible to near-IR, imaging from the near-UV to the near-IR with the point-spread function critically sampled at 6300 Å, and solar blind far-UV imaging. The primary design goal of the ACS Wide-Field Channel is to achieve a factor of 10 improvement in discovery efficiency, compared to WFPC2, where discovery efficiency is defined as the product of imaging area and instrument throughput. These gains are a direct result of improved technology since the HST was launched in 1990. The Charge Coupled Devices (CCDs) used as detectors in the ACS, are more sensitive than those of the late 80s and early 90s, and also have many more pixels, capturing more of the sky in each exposure. The wide field camera in the ACS is a 16 megapixel camera.

The ACS was installed during the March 2002 servicing mission. As a result of the improved sensitivity it instantly became the most heavily used Hubble instrument. It has been used for surveys of varying breadths and depths, as well as for detailed studies of specific objects. The ACS worked well until January 2007, at which time a failure in the electronics for the CCDs occurred and has prevented use of those detectors. Engineers and astronauts then developed an approach to remove and replace the failed electronics, which was carried out during the 2009 servicing mission. As with the STIS repair, the ACS repair was challenging, since the instrument was not designed originally with this type of repair in mind.

Learn More About ACS

Cosmic Origins Spectrograph (COS)

The Cosmic Origins Spectrograph (COS) is a fourth-generation instrument that was installed on the Hubble Space Telescope (HST) during the 2009 servicing mission. COS is designed to perform high sensitivity, moderate- and low-resolution spectroscopy of astronomical objects in the 115-320 nm wavelength range. It significantly enhances the spectroscopic capabilities of HST at ultraviolet wavelengths, and provides observers with unparalleled opportunities for observing faint sources of ultraviolet light. The primary science objectives of the COS are the study of the origins of large scale structure in the Universe, the formation and evolution of galaxies, the origin of stellar and planetary systems, and the cold interstellar medium.

The COS achieves its improved sensitivity through advanced detectors and optical fabrication techniques. At UV wavelengths even the best mirrors do not reflect all light incident upon them. Previous spectrographs have required multiple (5 or more) reflections in order to display the spectrum on the detector. A substantial portion of the COS improvement in sensitivity is due to an optical design that requires only a single reflection inside the instrument, reducing the losses due to imperfect reflectivity. This design is possible only with advanced techniques for fabrication, which were not available when earlier generations of HST spectrographs were designed.

COS has a far-UV and near-UV channel that use different detectors: two side-by-side 16384 x 1024 pixel Cross-Delay Line Microchannel Plates (MCPs) for the far-UV, 115 to 205 nm, and a 1024x1024 pixel cesium telluride MAMA for the near-UV,170 to 320 nm. The far-UV detector is similar to detectors flown on the FUSE spacecraft, and takes advantage of improved technology over the past decade. The near-UV detector is a spare STIS detector.


Learn More About COS

Space Telescope Imaging Spectrograph (STIS)

A spectrograph spreads out the light gathered by a telescope so that it can be analyzed to determine such properties of celestial objects as chemical composition and abundances, temperature, radial velocity, rotational velocity, and magnetic fields. The Space Telescope Imaging Spectrograph (STIS) can study these objects across a spectral range from the UV (115 nanometers) through the visible red and the near-IR (1000 nanometers).

STIS uses three detectors: a cesium iodide photocathode Multi-Anode Microchannel Array (MAMA) for 115 to 170 nm, a cesium telluride MAMA for 165 to 310 nm, and a Charge Coupled Device (CCD) for 165 to 1000 nm. All three detectors have a 1024 X 1024 pixel format. The field of view for each MAMA is 25 X 25 arc-seconds, and the field of view of the CCD is 52 X 52 arc-seconds.

The main advance in STIS is its capability for two-dimensional rather than one-dimensional spectroscopy. For example, it is possible to record the spectrum of many locations in a galaxy simultaneously, rather than observing one location at a time. STIS can also record a broader span of wavelengths in the spectrum of a star at one time. As a result, STIS is much more efficient at obtaining scientific data than the earlier HST spectrographs.

A power supply in STIS failed in August 2004, rendering it inoperable. During the servicing mission in 2009, astronauts successfully repaired the STIS by removing the circuit card containing the failed power supply and replacing it with a new card. Since STIS was not designed for in-orbit repair of internal electronics, this task was a substantial challenge for the astronaut crew.

Learn More About STIS


Wide Field Camera 3 (WFC3)

The Wide Field Camera 3 (WFC3) is also a fourth generation instrument that was installed during the 2009 servicing mission. Equipped with state-of-the-art detectors and optics, WFC3 provides wide-field imaging with continuous spectral coverage from the ultraviolet into the infrared, dramatically increasing both the survey power and the panchromatic science capabilities of HST.

The WFC3 has two camera channels: the UVIS channel that operates in the ultraviolet and visible bands (from about 200 to 1000 nm), and the IR channel that operates in the infrared (from 900 to 1700 nm). The performance of the two channels was designed to complement the performance of the ACS. The UVIS channel provides the largest field of view and best sensitivity of any ultraviolet camera HST has had. This is feasible as a result of continued improvement in the performance of Charge Coupled Devices designed for astronomical use. The IR channel on WFC3 represents a major improvement on the capabilities of the NICMOS, primarily as a result of the availability of much larger detectors, 1 megapixel in the WFC3/IR vs. 0.06 megapixels for the NICMOS. In addition, modern IR detectors like that in the WFC3 have benefited from improvements over the last decade in design and fabrication.

Learn More About WFC3

The Fine Guidance Sensors (FGS)

The Fine Guidance Sensors (FGS), in addition to being an integral part of the HST Pointing Control System (PCS), provide HST observers with the capability of precision astrometry and milliarcsecond resolution over a wide range of magnitudes (3 < V < 16.8). Its two observing modes - Position Mode and Transfer Mode - have been used to determine the parallax and proper motion of astrometric targets to a precision of 0.2 mas, and to detect duplicity or structure around targets as close as 8 mas (visual orbits can be determined for binaries as close as 12 mas).


Learn More About FGS

Previously Operational Instruments

Please Contact the HST Help Desk with any Questions