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Coarse Sun Sensor (CSS)

      

The coarse sun sensor assembly consists of two identical half sphere sensors, providing complete 4 tex2html_wrap_inline16425 steradian sun direction information. Each sensor provides angle information of the sun line with respect to two perpendicular axes.

The spacecraft coordinate system is right handed ( tex2html_wrap_inline16427 ). The tex2html_wrap_inline16429 axis points towards the sun within tex2html_wrap_inline16431 20 tex2html_wrap_inline16433 . 

The symmetry axis of the sensors is mounted in-line with the - tex2html_wrap_inline16435 axis and + tex2html_wrap_inline16437 axis, respectively. The sensor outputs correspond to one angle in the tex2html_wrap_inline16439 -plane and one angle in the tex2html_wrap_inline16441 -plane with nominal zero output when the sun is in the - tex2html_wrap_inline16443 or - tex2html_wrap_inline16445 direction.

The sensitivity for the inner region ( tex2html_wrap_inline16447 0.1 rad) is of the order of 100 mV/rad within either of the symmetry planes ( tex2html_wrap_inline16449 -plane or tex2html_wrap_inline16451 -plane of the sensor). The output is a monotonic characteristic between -83 tex2html_wrap_inline16453 and +83 tex2html_wrap_inline16455 . Between 83 tex2html_wrap_inline16457 and 97 tex2html_wrap_inline16459 the characteristic decays linearly to zero.

 

 

Range 4 tex2html_wrap_inline16461
Zero bias error tex2html_wrap_inline16463 0.50
Tolerances on 83 tex2html_wrap_inline16465 , 97 tex2html_wrap_inline16467 points tex2html_wrap_inline16469 10
Tolerances on output voltage tex2html_wrap_inline16471 5% when illuminated with 1 solar constant
Table 1.2: Performance of the ROSAT coarse sun sensor

 

The measurement performance parameters are given in Tab. 1.2.

After the Y-gyro loss,    the CSS has been used for coarse target acquisition. A software patch in the AMCE was designed and tested, and has been in operation since the start of 1991 October. After the Z-gyro loss in 1993 October,   the CSS has been used together with the magnetometer,  the S-gyro,   and the degraded X-gyro for attitude control.  


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Next: Magnetometer Up: 1.2 Payload Description Previous: South Atlantic Anomaly Detectors

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