Don't get lost!

-June 10, 2013

My trip to Finland last month was very stressful as bad weather delayed the delivery of some test equipment that I had previously sent to Jyvaskyla. I spent much of the day before our flight tracking my crate on the UPS website hoping to see some movement: the prospect of my colleagues and I arriving at the cyclotron without our instruments and having to explain this to the customer filled me with fear.

During the flight to Helsinki, I needed to calm down and started writing this blog. Every so often, I would look up and follow the display tracking our journey, reporting altitude, speed and the estimated arrival time. I love satellite navigation (Sat. Nav)! It’s a real, tangible example of what our industry has developed that has improved the quality of all our lives - my wife thinks I am no longer able to read a map!

Sat. Nav. will soon impact air travel in a more radical way than navigation and EGNOS/WAAS/LAAS-assisted landing. Iridium’s LEO constellation of NEXT satellites will contain a hosted payload that will supplement traditional, ground-based, RADAR tracking of aircraft. Instead of using RADAR to interrogate aircraft and determine their positions, each plane will use GPS to find its own position and automatically report this via the IGAM (Iridium Global Aviation Monitoring) secondary payload. Following processing of the ADS-B data, navigation reports will be sent down to air-traffic control using the main NEXT mission transmitter. The position of the IGAM hosted payload on the spacecraft is the yellow box highlighted below:

Artist’s impression of IGAM hosted payload on the Iridium LEO spacecraft.

Given the projected increases in future air travel, many countries will require all aircraft entering their airspace to be equipped with some form of ADS-B transmitter.

An equivalent, space-based tracking system to monitor maritime traffic is currently being tested. Ninety percent of the world’s commerce moves by sea, and companies such as ExactEarth and Orbcomm offer LEO, satellite-based monitoring of global shipping.

Currently, 60,000 vessels are fitted with a VHF transponder to inform other ships, port authorities, naval forces and coast guards of their current position. This traditional, line-of-sight, RF tracking is limited to approximately 50 nautical miles because of the curvature of the Earth. Satellite-based Automatic Identification System (S-AIS) allows full visibility of maritime traffic as well as offering other services such as security, surveillance, environmental protection and search & rescue. The map below was created from the AIS-data collected during a polar orbit.

S-AIS map showing maritime traffic steering clear of the Somali coast to avoid pirates.

Recent advances in remote sensing include GNSS Reflectometry which derives information about Earth by processing navigation signals that have been reflected off the planet’s surface and subsequently received by a satellite.

The UK-DMC satellite, part of the Disaster Monitoring Constellation built by Surrey Satellite Technology Ltd, carries a payload that has demonstrated the feasibility of receiving and measuring GPS signals reflected from the surface of the Earth's oceans to determine wave motion and windspeed.

I’d love to hear of other novel uses of Sat. Nav. Until next month, don’t get lost!

P.S. I’ll be presenting a webinar this Thursday at 07:30 PDT at the Xilinx Radiation Test Consortium on Hardware Design Considerations when using the V5QV FPGA for Spacecraft Avionics.

See you on-line!

Loading comments...

Write a Comment

To comment please Log In