HackSat One Orbit
HackSat One will start out in a similar orbit to the ISS. The ISS is in low earth orbit (LEO), with an orbital period of a little over ninety minutes. At 30 July 2013, the ISS orbital parameters are 414 x 419 km, 51.6°. Due to drag, HackSat's orbit will decay over a period of 2-6 weeks. The uncertainty in the decay time is due to solar activity affecting atmospheric conditions.
London ISS Passes
Given the initial HackSat orbit, we can use predictions of ISS passes to give us an idea of when we might be able to receive a signal at our London ground station; at least in the first week or so. In order to receive a signal the satellite needs to be above the horizon and in sunlight. Due to being in LEO, the shadow of the Earth affects a significant proportion of the passes over London in winter.
The following table shows ISS passes in London in the two weeks after the currently scheduled launch date (9th December). Only passes in which the ISS is at least 20º above the horizon and spends a significant part of the pass in sunlight are shown. Particularly favourable passes, those closer than 520 km and over four minutes long, are highlighted in green. Note how there are no usable passes until five days after launch. See below table for explanatory notes.
It's important to note that these predictions will change significantly in the run up to the launch. The ISS orbit is affected by atmopheric conditions and has its orbit boosted to keep it at the desired height. See graph of mean ISS height.
| Date/Time | Length | Alt | Dist | Sun Alt |
|---|---|---|---|---|
| 14/12/2013 17:42 | 3m57s | 38º | 651 | -16.1º |
| 15/12/2013 16:52 | 5m35s | 27º | 840 | -8.9º |
| 16/12/2013 17:38 | 4m28s | 62º | 470 | -15.4º |
| 17/12/2013 16:48 | 6m19s | 46º | 566 | -8.2º |
| 18/12/2013 15:58 | 6m04s | 33º | 722 | -1.6º |
| 18/12/2013 17:34 | 4m44s | 85º | 420 | -14.7º |
| 19/12/2013 15:07 | 5m24s | 23º | 932 | +4.2º |
| 19/12/2013 16:44 | 6m41s | 72º | 440 | -7.5º |
| 19/12/2013 18:20 | 2m53s | 64º | 463 | -21.6º |
| 20/12/2013 15:53 | 6m33s | 55º | 502 | -1.0º |
| 20/12/2013 17:30 | 4m57s | 85º | 421 | -14.0º |
| 21/12/2013 15:03 | 6m08s | 40º | 623 | +4.8º |
| 21/12/2013 16:40 | 6m41s | 89º | 419 | -6.9º |
| 21/12/2013 18:16 | 3m12s | 73º | 436 | -20.8º |
| 22/12/2013 14:13 | 5m50s | 28º | 803 | +9.5º |
| 22/12/2013 15:49 | 6m40s | 80º | 425 | -0.3º |
| 22/12/2013 17:26 | 5m22s | 88º | 419 | -13.3º |
| 23/12/2013 13:23 | 5m00s | 20º | 1033 | +12.8º |
| 23/12/2013 14:59 | 6m38s | 65º | 453 | +5.3º |
| 23/12/2013 16:35 | 6m42s | 86º | 420 | -6.1º |
| 23/12/2013 18:12 | 3m45s | 50º | 537 | -20.1º |
- Data are based on Heavens Above for 29 July 2013 epoch.
- Date/Time and Sun Alt are at the time of maximum altitude in sunlight.
- Length is time above 10º altitude whilst in sunlight.
- Alt is the maximum altitude above the horizon in sunlight.
- Distance is closest approach to ground station in kilometres whilst in sunlight.