FOS Blue Detector Plate Scale and Orientation

Anuradha Koratkar

Space Telescope Science Institute

Instrument Science Report CAL/FOS087





ABSTRACT

Inilight plate scale factors for the FOS blue detector are measured
for the first time from tbe cycle 1 proposal ID number 3366 data. The
analysis indicates that the scale factors are 1.48±0.03 per diode
height and 0.368±0.01 per diode width. The uncertainity in the
analysis due to GIMP correction is of the same order as the difference
in the plate scale calculated from the present analysis and the
prelaunch specifications. Hence, the present prelaunch plate scale
factors of 1.43 perdiode height and 0.357 per diode width need not be
changed in the database.


A mean rotation angle of ~0.12o±O.37o is measured between the FOS Y
axis and the direction perpendicular to the diode array. Similarly, a
mean rotation angle of 2.03~+0.36~ is measured between the FOS X axis
and the direction parallel to the diode array. These negligiblely
small rotation angles indicate that tbe orientation of the diode array
is weil aligned with the FOS XY axes.