SPOT Trace – A Good Secondary Flight Beaconing System

SPOT LLC www.findmespot.com offers a relatively new tracking product called the “SPOT Trace.”  It is smaller, lighter, and less expensive tracking device than SPOT’s popular “Gen 3” unit.  The Gen 3 – and its predecessors, the SPOT 2 and SPOT 1  – has been frequently used solutions for balloon flight tracking.  However, the company’s newer Trace unit may become the new preferred SPOT product choice for balloonists.  The Trace sends GPS coordinate data just like the original SPOTs, but the product is simplified with elimination of emergency call and messaging functionality -- features totally unnecessary for balloon flight.  The Trace offers a lower up-front cost and lower annual subscription cost than the Gen 3.

Interestingly, the Trace is promoted by SPOT LLC as a theft recovery tool – allowing owners of motorcycles, boats, or other mobile assets to share the location of stolen property with law enforcement. But frankly, the product appears to have some severe limitations for this purpose as the satellite communications link depends on a fully unobstructed view of the sky. A stolen motorcycle simply parked under the canopy of trees will have tracking signals blocked. But for the purpose of balloon flight tracking the Trace unit – like the original SPOT – works well as the sky is in full view.

It is important to understand that both the Trace and the original SPOT products will stop communicating above approximately 21,000 feet.  As most balloon flights are planned to climb above 80,000 feet, a large portion of the flight path will not be reported. This is why SPOT products should be considered back-up location reporting systems.  A separate radio-based system, such as an APRS beacon, should be designed as the primary flight path reporting system – providing latitude, longitude, and altitude data for the entire flight.

The SPOT Trace can have a big benefit over a radio-based location system at the end of flight - touchdown. Once the payload is on the ground, radio-based beaconing (e.g., APRS) will very likely no longer have a line-of-sight to transmit landing location to receiving stations. The APRS radio is too low to hit any receiving antennas. But the Trace unit is communicating via satellites, and so the landing location of the payload on the ground can still be sent – assuming the Trace is facing up and has an unobstructed view of the sky*. 

The following table shows a comparison of the SPOT Trace and SPOT Gen 3. 

	SPOT Trace	SPOT Gen 3	Trace Advantage
Product Cost	$99.99 + tax	$149.99	$50 Less
Annual Subscription Cost	$99.99 + tax	$149.99	$50 Less
Longitude, Latitude	YES	YES
Altitude	NO	NO
Weight with Batteries	90 grams	114 grams	24 grams
Size	2.69” x 2.02” x 0.95”	3.43” x 2.56” x 1”	Smaller
Primary Color	Black	Orange	Black absorbs more heat
Power Source	4 AAA Lithium	4 AAA Lithium
Max Altitude		21,320 feet
Max Reporting Frequency	5 minutes**	5 minutes**
Operating Temperature	-22F to +140F	-22F to +140F
Unnecessary Communication Functions	NO	YES	Simpler Design

** For an extra fee, the reporting frequency can be increased to once every 2 ½ minutes. 

Here is a map show some of the early (non-flight) testing location reporting by the Trace unit using a SPOT App:

*One method to greatly increase the odds of the Trace facing up is to place it inside a gimbal – a 3-axis device – that allows gravity to keep proper orientation.