I recently read the book, The Martian, by Andy Weir, and then watched the movie. I was fascinated by Mark Watney’s engineering efforts to communicate with Earth. There may be people who still intend to read the book or watch the movie, so I won’t spoil anything (more than I already have). The book/movie reminded me of a recent article in QST Magazine (December 2015, pg. 59) about the Elser-Mathes Cup, an award devised by Fred Elser and Stanley Mathes in 1929 to be given to the first hams to achieve an Earth to Mars QSO. The article, and the aforementioned novel, got me thinking about how our hobby would work on the red planet.
The New Horizons probe, that recently did a fly-by of Pluto, sends data across the more then three billion miles using an astonishingly paltry 12 watts of power at X-band frequencies (around 8 GHz). Of course for most of that journey there is no atmospheric attenuation or topographic obstacles to transmission, but still…the point is that massive power levels are not necessarily required to make an Earth-Mars QSO.
I also found a document produced by NASA in 2002 about radio communication on Mars. I haven’t read the whole thing (it’s 105 pages long, after all), but here’s an interesting tidbit:
“The Martian ionosphere is almost transparent to radio waves with frequencies above 450 MHz. For frequencies below 450 MHz, there is a progressive degradation of signal until the 4.5-MHz cut-off frequency where waves cannot pass through the ionosphere….The Martian dayside ionosphere has a critical frequency of ~4.0 MHz for vertical incidence. This frequency is high enough to carry information. The stable condition in the dayside ionosphere also favors oblique incidence communication. Reflection off the Mars ionosphere can also provide trans-horizon (or beyond line of sight) communication for future Martian colonies, rovers, vehicles, and robots released from Mars landers. However, because of low usable frequency and very unstable condition, the nightside ionosphere has serious limitations for global communication.” (page 95)
So it sounds like frequencies above our 70 cm band would be usable for getting from Mars to Earth; Mars Curiosity rover uses X-band transceivers to communicate directly with the Earth, and UHF transceivers can connect with relays on Mars-orbiting satellites. But what sort of receiver would one need to complete the QSO? The Deep Space Network uses 70-meter diameter dishes to receive New Horizon’s data. Mars is closer (about 10% of the current New Horizons probe distance), and hams could go above 12 watts transmit power, but still, I think very sensitive receivers and quality antenna arrays would be an obvious necessity.
In any event, the technology for very long distance DX is currently possible. The remaining challenge to awarding the Elser-Mathes Cup is getting a ham to Mars to make the QSO. And once that happens, the real challenge will be waiting the almost 30 minutes to get a reply to “Is this frequency in use?”
What gear will you be taking on a DXpedition to Olympus Mons? Share your thoughts in the comments…