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AO-40: Hibernation #2 - Final Report



                        AO-40 Hibernation #2
                        --------------------
                                 by
                        James Miller G3RUH

                            2001 Apr 30

AO-40 entered "hibernation", a period when the Sun sensors cannot see the Sun,
and magnetorquing is not possible, on 2001 Apr 08, for a 3 week period.

This hibernation differed in one important respect to that previous; in
hibernation #2 we had measurements of alon throughout from the Earth
sensors.  Through this it was discovered that the spacecraft experiences an
additional torque at perigee which re-orients it slightly.

Knowing this it was a straightforward matter to keep track of alon, the
"mystery effect", and by using the YACE camera on orbits 207, 216 and 225
measure alat, and thus create the Sun angle history, without actually having
a Sun sensor working.

Recordings were also made of a number of temperature points, and these
correlated sensibly with the estimated Sun angle.

The hibernation ended on orbit 228, exactly when expected.

Finally, attached is a plot of the temperatures, and appended the data
collected during hibernation.



ATTITUDE MEASUREMENTS:

  Orbit   alon alat                Orbit   alon alat
----------------------           ----------------------
  202     141        *            216     106   13   **
  203     138        *            217      -     -
  204     136        *            218     102        *
  205     133        *            219      -     -
  206     132        *            220      98        *
  207     128   14   **           221      95        *
  208     127        *            222      93        *
  209     125        *            223      90        *
  210     121        *            224      88        *
  211     119        *            225      85   12   **
  212     116        *            226      83        *
  213     114        *            227      81        *
  214      -     -                228      79        *
  215     109        *
----------------------           ----------------------
  *    alon based on ES stop(s)
  **   camera gives alon and alat

RMS error, fit on alon: 0.43°


ATTITUDE ESTIMATE and TEMPERATURE MEASUREMENTS:

       Attitude   | Batteries (deg.C)|   Tanks (deg. C)  |  (deg. C)  Panels
 Orbit lon/lat SA | Main2 Aux1  Aux5 | MMH-3 N204+  NH3-2| IHU   EPU    2-5
 -----------------+------------------+-------------------+------------------
 200          -41 | 29.8  33.1  21.1 | 19.3  17.3   31.8 |  9.4  19.9   9.0
 201          -43 | 31.1  35.1  21.9 | 19.9  18.6   33.1 | 10.0  21.2   7.1
 202  141  15 -47 | 33.8  37.1  22.6 | 20.6  19.3   35.7 | 10.0  21.9   1.8
 203  138  14 -49 | 35.1  39.0  23.2 | 21.2  20.6   37.1 | 10.0  22.6
 204  136  14 -51 | 36.4  39.7  23.9 | 21.2  21.2   38.4 | 10.0  23.2  -2.5
 205  133  14 -53 | 37.1  41.0  23.9 | 21.2  21.2   39.0 | 10.0  23.2  -4.5
 206  131  14 -56 | 37.7  41.7  23.9 | 21.2  21.2   39.7 |  9.4  23.2  -6.4
 207  129  14 -58 | 37.7  41.7  23.2 | 20.6  20.6   39.7 |  8.7  22.6  -8.4
 208  126  14 -59 | 37.1  41.0  21.9 | 19.9  19.3   39.0 |  8.1  21.9 -10.4
 209  124  14 -61 | 37.1  40.4  21.9 | 18.6  17.9   38.4 |  6.7  20.6 -13.7
 210  121  14 -62 | 36.4  40.4  21.2 | 18.4  17.3   38.4 |  6.1  19.9 -15.0
 211  119  14 -64 | 35.7  39.7  20.6 | 16.6  16.6   37.7 |  5.4  19.3 -17.0
 212  117  13 -65 | 35.7  39.0  20.6 | 16.6  16.0   37.7 |  4.8  18.6 -18.3
 213  114  13 -65 | 35.1  39.0  19.3 | 15.3  15.3   37.1 |  4.1  17.9 -19.6
 214  112  13 -65 | 35.1  39.0  19.9 | 15.3  14.7   37.1 |  4.1  17.9 -19.6
 215  109  13 -65 | 35.1  39.0  20.6 | 16.0  14.7   37.1 |  4.1  17.9 -19.6
 216  107  13 -65 | 35.1  39.0  20.6 | 16.0  14.7   37.1 |  4.1  17.9 -19.0
 217  105  13 -64 | 35.1  39.0  19.9 | 16.0  14.7   37.1 |  4.1  18.6 -18.3
 218  102  13 -63 | 35.1  39.0  20.6 | 16.0  15.3   37.1 |  4.8  18.6 -17.6
 219  100  13 -62 | 35.1  39.0  20.6 | 16.6  15.3   37.1 |  4.8  18.6 -16.3
 220   97  13 -60 | 35.7  39.0  21.9 | 17.3  16.0   37.7 |  6.1  19.9 -13.7
 221   95  12 -59 | 35.7  39.7  22.6 | 17.9  16.6   37.7 |  6.7  20.6 -12.0
 222   93  12 -57 | 36.4  40.4  23.2 | 19.3  17.3   38.4 |  8.1  21.2  -9.7
 223   90  12 -55 | 36.4  40.4  23.9 | 19.9  17.9   38.4 |  8.7  21.9  -7.8
 224   88  12 -52 | 37.1  41.0  24.5 | 21.2  19.3   39.0 | 10.0  23.2  -5.1
 225   85  12 -50 | 37.1  41.0  24.5 | 21.2  19.3   39.0 | 10.7  23.9  -3.1
 226   83  12 -48 | 37.1  41.0  26.5 | 22.6  19.9   39.0 | 11.4  24.5  -1.2
 227   81  12 -45 | 37.1  41.0  27.2 | 23.2  20.6   39.0 | 12.0  25.2   0.8
 228   78  12 -43 | 37.1  41.0  27.2 | 23.9  21.2   39.0 | 12.7  25.2   2.8
 -----------------+------------------+-------------------+------------------
 Rate of change of alon: -2.396°/perigee
 Precession rate:        -0.161
 --------------------------------------
 Mystery effect:         -2.235°/perigee at 2.05 - 2.01 rpm  and Hp ~ 315 km
 --------------------------------------

<end>

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