The video above is a quick screencast NASA JPL’s Eyes on the Earth application, which shows the tracks of various satellites orbiting the globe. It’s a really cool application that gives a top-notch overview of some of the satellites currently in orbit and their trajectories around the Earth. Take some time and poke around, you’ll be glad you did.
The reason I included it is that I promised to cover the polar orbiting satellite receiving station in a previous blog post about the new Satellite Receiving Station in Delaware. In the previous post I discussed the geostationary satellite receiving station. In this post, I hope to shed some light on the polar orbiting receiving setup.
What’s Inside the Radome
The equipment for the polar orbiting satellite receiving station is a bit more involved than the pretty much non-moving geostationary setup. As the name implies, the polar orbiting satellites do just that, they orbit the Earth north and south, going from pole to pole. Their path is relatively simple, they just go around the earth in circles, but as they’re doing so, the Earth is rotating beneath them. The satellites point their cameras towards the earth and essentially capture a swath of data during each rotation. Since the Earth is rotating beneath them, the swath appears as a diagonal path if you look at the overlay.
In order to capture data from a moving target, the dish has to be able to rotate and move in three axis in order to follow the satellite of interest. In order to protect the receiving equipment from the weather, it is typically installed in a circular fiberglass enclosure called a “radome”. To keep the design relatively simple, there is only one mounting configuration and radome setup created, and that’s designed to mount onboard a ship. It is then relatively simple to attach a mounting bracket to the top of a building and bolt the radome assemgly to it.
The video at the top of the page shows that there are several satellites in orbit, so the Terascan software has to pull down satellite ephemeral data from Celestrak each day, take into account the location of the tracking station, and generate a calculated schedule of which satellites will be visible to the satellite dish throughout the day. As there may be more than one satellite in view during any given time period, the satellite operator assigns a priority weighting to each satellite. The Terascan software then uses that weighting to decide which satellite it will aim the dish at and start capturing data.
Receiving Station Workstations
Inside the building is a rack of computers and receivers whose purpose in life is to control the dish on the roof of the building and to receive and process the data it relays down from the satellite. The receiving station at UD has both X and L-Band receivers which receive the data stream and pass it to a SeaSpace Satellite Acquisition Processor. The processor then sends the data packets to a Rapid Modis Processing System (RaMPS) which combines the granularized HDF data files from the satellites into a TeraScan Data File (TDF) file. Once in this format, various programs and algorithms can be run against the TDF file and channels of interest can be combined using NASA/NOAA and other user supplied algorithms to create the output product of interest. As the files can get rather large and there can be several of them coming in throughout the day, they are then moved over to a Networked Attached Storage (NAS) server and stored until they are needed.
Satellites Licensed
The UD receiving station is licensed and configured to receive data from the following satellites:
- Aqua
- Terra
- NOAA 15
- NOAA 17
- NOAA 18
- NOAA 19
- MetOp-A (Europe)
- FY-1D (China)
Hopefully this sheds a little more light on the polar orbiting receiving station and its capabilities. Let me know if there are any additions or corrections to the information I’ve posted.