Reach for the stars
26 May 2009
Hubble space telescope gets an upgrade including new CCD cameras that span UVIS to NIR.
The Hubble Space Telescope first went into orbit in April 1990, and uses it position above the Earth’s atmosphere (which distorts and blocks light reaching our planet), to give a view of the universe that can surpass that of ground-based telescopes. Hubble has beamed thousands of images back to Earth and uncovered many mysteries of the universe. NASA is now undertaking a final mission to repair and upgrade the telescope. The mission, designated STS-125, will equip the telescope with new equipment including Charge Coupled Device (CCD) imaging sensors from e2v.
The new sensors will be launched into space by NASA on board the space shuttle Atlantis, as part of a mission to upgrade and repair the Hubble Space Telescope. e2v CCD imaging sensors will equip Wide Field Camera 3 (WFC3), a new instrument that will be installed on Hubble to take large-scale, extremely clear and detailed pictures of the universe over a very wide range of colours.
WFC3 will replace the existing Wide Field Planetary Camera 2 (WFPC2). Its key feature is the ability to span the electromagnetic spectrum from the Ultra-Violet (UV), through visible/optical light and into the Near Infra-Red (NIR). It is this wide-field ‘panchromatic’ ability that is so unique and gives WFC3 the ability to observe young, hot stars (glowing mainly in UV) and older, cooler stars (glowing mainly in red and NIR) in the same galaxy, and more than a 10 times improvement over WFPC2 in discovery efficiency at UV wavelengths. WFC3 is able to do this through its dual-channel design using two sensor technologies. Incoming light is beamed from the telescope to either the Ultra-Violet-Visible (UVIS) channel or the Near-Infrared (NIR) channel. The UVIS channel of the instrument is equipped with e2v’s large CCD-43 imaging sensor.
Specifications for the imaging sensor are as follows:
*Large area, with around 4k(H) by 2k(V) 15 micron pixels.
*Full frame imaging CCD designed to operate in Inverted Mode for low dark signal.
*Enhanced Ultra-Violet quantum efficiency and back-illumination to give a very broad waveband response. The typical quantum efficiency is 50% at 250 nm and 65% at 500 nm.
*Designed and packaged for assembly in close-butted pairs, typically 250 µm (with a specification at 340 µm) per chip, i.e.~500 µm if butted, thus creating a ~4k square image area.
*The two high-responsivity and very low noise output amplifiers, typically ~2.5 e-rms at 50 kHz, on each sensor, enable imaging of feint objects.
*A parallel charge injection structure permits mitigation against radiation effects of the space environment and a supplementary “notch” or mini-channel is included to further reduce the impact of irradiation when imaging at small signal levels.
*The readout register has a gate controlled dump drain to allow fast dumping of unwanted data.
Brian McAllister, General Manager of Space & Scientific Imaging at e2v, said “This is a prime example of how our e2v sensors are being used to accelerate discovery, by upgrading the performance of the Hubble Space Telescope’s vision to reach previously unexplored territory.”
Dr Randy Kimble, WFC3 Instrument Scientist at NASA's Goddard Space Flight Center said "We have been very pleased to work with the exceptionally talented folks at e2v to bring this technology to the Hubble Space Telescope. It will enable significant advances in large-format ultraviolet and visible observations to provide new discoveries about the nature of our universe."
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