Science Objective
Instrument description summary
Polar Mission
Instrument basic parameters
UVI Camera UVI Electronic Stack (control electronics)
UVI Mechanical/Thermal Design
Return to the UVI Home Page
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The Ultraviolet Imager (UVI) is a small sophisticated camera, which from Earth orbit, will detect and produce images of the ultraviolet light of the aurora, day and night. As such, it is one of eleven instruments onboard the Polar spacecraft, which is the second mission of NASA's Global Geospace Science (GGS) Program.
The UVI is able to detect and provide images of very dim emissions with a wavelength resolution never achievable before. The highly sensitive instrument will conduct observations of the polar aurora in the far ultraviolet wavelengths and help quantify the overall effects of solar energy input to the Earth's polar regions. Its scientific objectives are to image to aurora simultaneously, to measure the total energy and characterize the energy that is deposited in the auroral regions, to characterize the space and time variations of the aurora, and to correlate events in the auroral regions to other regions in the magnetosphere.
Energetic particles, including electrons and protons, emanate from the Sun comprising what is called the solar wind. As these particles stream by the Earth at speeds up to one million miles per hour, they are redistributed and accelerated by the Earth's magnetic field in a region of space known as the magnetosphere. This redistribution of solar energy results in channeling large amounts of energy, equivalent to as much as 100 million kilowatts of energy each day, down into the Earth's atmosphere in the polar regions. These energetic particles collide with the elements of the upper atmosphere at altitudes between 90 and 150 kilometers resulting in the emission of light known as the aurora. The aurora can be thought of as the "footprint" of events and energetic processes occurring in the Earth's magnetosphere.
The objective of the Global Geospace Science Program is primarily three fold: To measure the energy and particle flow from the Sun into the Earth's magnetosphere and atmosphere and how the flow changes in time; To improve the understanding of the processes that determine this flow; and To determine the importance of the variations of this flow to the Earth's atmosphere.
The Ultraviolet Imager (UVI) consists of a camera and an electronic support package known as the Electronic Stack. The UVI is a two dimensional spatial imager which produces images of the Earth's auroral regions in the far ultraviolet wavelength range (130nm to 190 nm). Using any of five specially designed filters the UVI camera will image an eight degree circular field of view. Images are generated once every 37 seconds with an angular resolution of 0.036 degrees. The Electronic Stack monitors the status of the camera, controls the mechanical components and serves as the electrical interface with the spacecraft. UVI weighs 21 kilograms, uses 21 watts, and has a telemetry output of 12 kbps. The overall sensitivity of the instrument is about 10 Rayleighs which is equivalent to being able to detect objects more than 100 times fainter than the eye can see.
The UVI was manufactured, assembled and tested at Marshall Center in a joint effort with the University of Alabama in Huntsville, Ala. and Science and Engineering Associates in Huntsville.
For more detailed information on the Ultraviolet Imager instrument,
go the top of the page and click on the instrument
subsystem of interest. Also, look up the following paper:
The UVI is one of 11 scientific instruments launched with the
GGS/Polar spacecraft on a Delta II rocket from Vandenberg Air
Force Base, Calif. on February 23rd 1996. The Polar space craft
weighs 1,0050 kilograms (2,216 pounds) and carries some 269 kilograms
(593 pounds) of propellant for orbit and attitude control. The
design life of the Polar spacecraft is three years. GGS is managed
by NASA's Goddard Space Flight Center (GSFC), Md., for the Office
of Space Science at NASA Headquarters in Washington, DC Data collected
by the spacecraft is disseminated to the UVI investigation team
at Marshall Center from GSFC's Central Data Handling facility.
Detailed analysis is performed and data is shared through the
NASA Science Internet connections throughout the United States,
Japan and Europe. More detail about the Polar mission is available
on the Polar home page.
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| Wavelength range (five filters) | 130-190 nm |
| Focal Length | 124 mm |
| f/# | 2.9 |
| Full aperture | 12.13 cm sq |
| Full solid angle | 1.53e-2 (sr.) |
| Field of view (full angle) | 8 Degrees |
| Number of spatial elements | 36728 |
| Size of spatial elements at photocathode | 74x87 m |
| Typical sensitivity per spatial element at photocathode | 0.1 (Photoelectrons/R/37 s) |
| Angular resolution | ~0.036 Degrees |
| Data rate | 12Kpbs |
| Power | 21 Watts |
| Mass | 21 Kg |
