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High Speed Photometer

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Measures the brightness of an object, either within a particular
wavelength or throughout the entire spectrum; detects fluctuations.
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     The High Speed Photometer .~ (fig. 4)~ is designed to provide
accurate observatons of the total light from an object in space, note any
fluctuations in brightness on a time scale down to microseconds, and to
detail any fine shapes or structures associated with the light source.
These measurements are made over a wide spectral interval, including the
ultraviolet.


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     It is the simplest instrument of the group, containing no moving
parts, and relies entirely on the pinpoint accuracy of the spacecraft's
 .~ fine guidance sensors~ to accomplish its work.  After the light of a
star or other source is received, a .~ detector~ can measure either the
total brightness or the intensity of light within a particular portion of
the spectrum.


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     The High Speed Photometer, in addition, will transmit accurate
information on fluctuation in brightness over time. Detection of
rapidly spinning neutron or other compact stars will be possible,
as well as detailed data on the shape and structure of the fine
spikes or flares often associated with such compact objects.


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     The instrument will also be of special value to astronomers in
establishing calibration standards for faint stellar objects.