SOHLA

SOHLA-1 FSS Hi-mode analysis

SOHLA-1 FSS Hi-mode analysis
FSS ... Osaka Prefecture [Furitsu] University Sun Sensor
TSA ... Total Sun Angle

On 8 July 2009, SOHLA-1 performed the data acquisition by FSS Hi-mode for the
first time. Our Grand Station mention the analysis result in this page.


What's Hi-mode?

Hi-mode is the mode which measures data once in 0.2 second when we easily say.
Because the data measurement interval is large with the normal mode, it was
not able to measure TSA precisely. We can expect good analysis of the precision
in measuring data by Hi-mode use.


The number of the acquired data

Hi-mode is carried out for about 1 minute. The number of the data which we were
able to acquire this time are 285. There were not many omissions of data, and
it was very good data. We thank the satellitor who offered reception data!


Measurement result of Sun Angle (TSA)

The time change of TSA in the Hi-mode measurement became the following graphs.




FSS cannot measure TSA precisely unless the sun comes in the front. The reason
why TSA changes like a parabola is the changes of the sun position that looked
at from FSS by the spin of the satellite. We read a value of a top becoming a
parabola how to read right TSA from these data. In this time TSA was 41-43[deg].
By the way, it's as follows when we messure this graph with the normal mode.




Because the data lack like above, it become like this. Because receiving a data
once a second, it become the considerably coarse graph.

Note: We made the graph of the nomal mode for one minute to do comparison with
the Hi-mode. Actually we acquire the normal mode data for several minutes.
In addition, these above data were the data which they measured on another day.


Linear sensor output value

We will see how the linear sensor output value changes. We converted 64 sensor
data into the decimal number and took the average of the value. We will see
the graph which chased a change in that time. At first it's as follows when we
measure with the normal mode.




It's square-built like above and we are hard to somewhat imagine form. Because
there is a certain value between a point and a point, actually it is not good
to link between the data in a line. We seem to be able to confirm that the
sensor output value rises when the sunlight shines. Then it's as follows when
we measure with the Hi-mode.




Oh, it is a very beautiful graph! As is expected, it is connected smoothly
because it is the data which it take every 0.2 second. When the sunlight shines
the output value of the sensor suddenly rises. And there is the part that the
output value slightly rises. It is thought that FSS caught reflected light from
the earth.


Spin rate

We notice that there is a rhythm for the change when we see the above graph of
the sensor output value. We calculate the spin rate by measuring this period.
When we expressed the time change of the spin rate that it measured with a Hi-
mode, it became the following graphs.




The spin rate when we measured it this time was 5.56 rpm on an average.


Conclusion

The measurement of the Hi-mode can do the good measurement of the precision
more than the normal mode. However, the time when we can measure it is limited
because we can use Hi-mode in specifications of machinery only for one minute.
We carry out Hi-mode use in future and will perform more detailed analysis.


Supplement

SOHLA-1 Telemetry Decoder supported Hi-mode, Ver1.2 (13Jul2009)
http://www.dk3wn.info/files/sohla.zip