Footpoints show the end-points of the magnetic field lines on which the spacecraft is located. We use the Tsyganenko T96 model to follow field lines from the spacecraft position to each hemisphere.
The spacecrafts appear to perform a loop during each apogee: this is due to the spacecraft velocity falling below the Earth's rotation speed. The animation below shows the spacecraft (represented by a black dot) as it orbits the Earth and crosses magnetic field lines (in blue) over 24 hours. We also show the spacecraft footpoints.
It should also be noted that spacecraft B laps over A once each 2.5 month.
SuperDARN - Van Allen Probes Coordination
A page for items relating to the coordination of SuperDARN radar observations with the Van Allen Probes (formerly the Radiation Belt Storm Probes, a.k.a. RBSP).
SWG Telecon - Apr 26 - Ruohoniemi
SuperDARN - Van Allen Probe Conjunctions
VAP Footpoint Plots - Rob Fear
Source: Rob Fear, University of Leicester, UK
|Spacecraft footpoints in the ionosphere||what is this? (Movie)|
Note: Older versions of Internet Explorer will not display the foot-point map properly if at all... However you can obtain a pdf version by clicking the "Download PDF" button.
Note on ISR fields-of-view: FoVs are estimated based on a minimum elevation (6 degrees for MHO, 20 for EISCAT and 25 for all other ISRs) and a maximum altitude of 500km.
Footpoints of the Van Allen Storm Probes are calculated at 5-minute intervals from the ephemeris published at vanallenprobes.jhuapl.edu.
Each footpoint is obtained by following geomagnetic field lines from the low-inclination equatorial orbit of the spacecrafts down to the ionosphere (at an altitude of 300 km). This tracing is performed using Tsyganenko's T96 model with default quiet geomagnetic conditions (Dst Index : -5 nT, solar wind dynamic pressure : 2 nPa, IMF-By : 0 nT, IMF-Bz : -5 nT).
Note that ephemeris from vanallenprobes.jhuapl.edu are intentionally degraded to a single decimal digit due to NASA policy. However, this does not affect the foot-points in any significant ways.
The code used to generate these maps can be downloaded here: https://raw.github.com/sdelarquier/code/master/rbsp/rbsp.py
The T96 code and default values used to calculate these footpoints are freely available here: github.com/sdelarquier/tsyganenko
You can also see a more interactive view of these footpoints at http://rbspd3.herokuapp.com
If you have any questions or comments about the content displayed on this page, please contact us.
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