ARISS APRS operating again
After a long outage. the APRS (Automatic Position Reporting System)
aboard the International Space Station (ISS) is again operating, as may
be seen at <http://www.ariss.net/>.
On the Arlington County Net yesterday, I announced an imminent pass of
the ISS over Arlington starting 23:51:5 UTC (7:51:59 pm EDT) and lasting
10 minutes 49 seconds. This prediction was generated by my Debian
(debian dot org) package gpredict using Keplerian elements ("keps")
updated yesterday. However, two stations reported that they tried to
hear, but did not hear, the ISS APRS downlink.
This often happens when the ISS maneuvers (firing its engines) or docks
or undocks a supply or crew spacecraft (these actions change the mass
and the area, hence the drag, of the ISS, and hence the data on which
orbital predictions are based.) The lesson here is to be skeptical of
predictions and the data on which the predictions are based: are they
Here are some links that may help:
<https://spaceflight.nasa.gov/realdata/sightings/SSapplications/Post/JavaSSOP/JavaSSOP.html>: a NASA-recommended Java application for predicting sighting opportunities for the space station, which are passes of the ISS when the ISS may be seen, if skies are clear. This does not predict all passes of the ISS when the ISS may be heard or contacted by Amateur Radio.
NASA's predictions of passes of the ISS over Arlington, at times when it
may be seen (if clouds do not intervene).
<http://gpredict.oz9aec.net/documents.php>: Documentation for the GNOME
Predict (gpredict) application I use on Debian (debian dot org). This
predicts all passes, visible or not.
Enuf for now.
Science matters. Matter matters.
Energy matters, including dark energy.