Can HAM signals bouncing off the ionosphere really find the Malaysian Airlines MH370 crash site?

The Australian edition of the TV show 60 Minutes recently aired a piece involving retired British Aerospace engineer Richard Godfrey who says he knows where the Malaysian Airlines Flight MH370 went down eight years ago. Godfrey told 60 Minutes he used an amateur radio technology called Weak Signal Propagation Reporter (WSPR) to track the airliner’s path via signal disturbances.

Immediately after the broadcast there was a lot of pooh-poohing of the idea that WSPR records can be useful this way. In actuality, Godfrey first presented his ideas in May 2021, and debate about them has raged since then. Here’s a brief explanation of WSPR and how Godfrey says he uses it (along with some satellite data) to predict the crash site. We’ll also cover some of the main objections to the theory.

WSPR is actually a protocol, implemented in a computer program, used to find radio LF, MF and HF-band propagation paths between amateur radio operators. In a nutshell, a HAM operator hooks his or her transceiver to a computer running the program, then tells the program to set up a frequency shift keyed transmission carrying the operator’s callsign, Maidenhead grid locator, and transmitter power in dBm. The program tells the transceiver to broadcast this message and also to listen for similar messages from other operators. It can decode incoming signals with a signal-to-noise ratio as low as −28 dB in a 2,500 Hz bandwidth. Operators with internet access can automatically upload their reception reports to a central database called WSPRnet, which includes a mapping facility.

WSPRnet data goes back to 2008. The key development that gave credence to the idea of detecting MH370 with WSPRnet data was a study by Robert Westphal in Germany who detected several aircraft in Antarctica such as a B787-9, two Dassault Falcon 900EX, an Ilyushin IL76TD and a DC3C commuter airplane via WSPR tests. Westphal said testing in Antarctica was preferred as a way to avoid ambiguities with other aircraft as can happen in crowded air space. Westphal also was able to realize detection ranges of more than 7,500 km from Antarctica to New Zealand.

Westphal suggested a similar approach for MH370 because data about it is recorded in the WSPR database for the the entire eight-hour flight with signals from 7 MHz to 28 MHz, with signals coming from operators in Europe, Asia, North and South America as well as Australia and New Zealand.

Godfrey says the WSPR database contains 91,058 spots and 11,753 unique transmitter receiver links. Often transmitters will automatically send multiple transmissions at the same time which are picked up by over 20 different receivers around the globe. Godfrey says it is possible to see signal anomalies in this data over the timeframe of MH370 and on other days before and after the MH370 timeframe, as well as across the globe from the same transmitter at a particular time. The transmitted power ranges from 0 dBm to 50 dBm; the frequency bands range from 1 MHz to 28 MHz, the propagation distance ranges from 500 km to 19,437 km and the SNR ranges from – 33 dB to + 17 dB. Each transmitted power and each frequency band has to be treated separately. Each transmitter and each receiver and each link between them has to be treated separately. There are different antennas used and different terrain profiles at each location.

In addition to the WSPR data, Godfrey says he uses operational Automatic Dependent Surveillance–Broadcast (ADS–B) data of all aircraft in the Kuala Lumpur Flight Information Region during the MH370 time frame. This is a surveillance technology in which an aircraft determines its position via satellite navigation or other sensors and periodically broadcasts it, enabling it to be tracked. A spreadsheet models the MH370 flight path and the Inmarsat satellite data, the satellite ephemeris, the weather in the Indian Ocean and the Boeing 777-200ER fuel consumption. Matlab is used for the graphical presentation of the MH370 flight path. Finally any candidate detection is entered into HF propagation software called Proplab Pro V3.1. This software collects space weather data from scientific sources on the internet to model the ionosphere with its different layers via ray tracing. The ray tracing process gets complicated: The ionosphere exhibits a high granularity and some of its layers tilt. In his blog posts, Godfrey implies he checks each propagation path in the database for its maximum usable frequency, elevation angle, number of hops, interim landing points and proximity to the position of MH370 or other aircraft. Only once a detection candidate passes all the tests does he use it as an indicator to determine the position of MH370.

Godfrey calls the process outlined above GDTAAA (Global Detection and Tracking of Any Aircraft Anywhere). GDTAAA comprises the code generator that produces data for the Matlab function, the import of Matlab scripts for the relevant timeframe and the Matlab template script for graphical presentation. The software architecture comprises the WSPRnet data exported to Microsoft Excel, the ADS-B data exported to Microsoft Access, the Flight Path Model in Microsoft Excel, the Template Generator in Matlab R2021b, the Function Call Code Generator in Microsoft Excel and imported into the Matlab Script produced by the Template Generator and executed in the Matlab Function and the Propagation Path Analysis in Proplab Pro V3.1. Godfrey says te analysis of the GDTAAA output and the analysis of the Proplab Pro V3.1 output is manual.

Criticisms of Godfrey’s method generally center on the WSPR path accuracy. Some say deductions from WSPR data would only be true for paths traveling less than about one-third of the way around the globe. The mental exercise that shows the problem is to assume there are WSPR transmission and reception sites exactly 180° apart at specific points on the Earth that are directly opposite each other. There is no shortest path, and a signal would likely have followed the more highly ionized layers related to the terminator and Earth’s magnetic field lines. The potential flaw in the analysis lies in assuming the signal is equally likely to follow an extension of the shortest great circle path that only takes the long way around the Earth.

Critics say there was only one short global WSPR path during the MH370 flight. They claim that all the others in Godfrey’s analysis were long-path projections that just happen to confirm his candidate crash site. They further claim there can be no expectation of any accuracy for paths going three-quarters of the way around the globe. In a nutshell, critics say that Godfrey’s method needs a regular stream of signal reports to work, and that stream can only come from the shortest of global paths. But at the same time, the analysis assumes that each contact signal has taken the longest possible path around the globe via numerous skips, yet retaining the accuracy of a single skip or two.

Of course, today the arguments for and against Godfrey’s analysis are all theoretical. The proof will be either a crash site or the bottom of the ocean with nothing on it but sand.