“I can turn on the radio right now and be inspired.” — Courtney Love
One of the best-kept secrets on the International Space Station (ISS) is an inconspicuous mess of metal boxes and associated cables mounted on an already busy corner of the European Columbus Laboratory Module. This mess of electronics — also known as the Kenwood TM-D710E — is an amateur radio transceiver installed for the purposes of communicating back to Earth. The Kenwood’s intended audience is not Johnson Space Center however, but rather, everyday folks like you and me. It is in truth no secret that astronauts are regularly available to chat with their Earth-bound counterparts; in fact, NASA publicizes this opportunity regularly on their website. With some basic radio equipment, a little astrodynamics know-how, a license from the Federal Communications Commission (FCC), and lot of luck, you too can communicate with astronauts in space.
Astrodynamics is the study of artificial bodies (the ISS) moving under the influence of gravity from one or more large natural bodies (the Earth). Astrodynamicists apply physics to determine the trajectory of satellites, space telescopes, rockets, and other objects in space. Spacecraft often fall into orbit, a gravitationally curved trajectory around another object. Just as the Moon and ISS orbit around the Earth, the Earth orbits around the Sun. Astrodynamics allows engineers to determine where exactly spacecraft will be along an orbit at a given time. This in turn permits the calculation of spacecraft ground track, or where the spacecraft is located above the Earth. The best opportunity to contact the ISS is when it is directly overhead. Skip the math and head to European Space Agency ISS Tracker website to determine when the ISS will next be over Douglasville, GA. The ISS is in Low Earth Orbit, meaning it is roughly 1,200 miles above the Earth’s surface, and that it circumnavigates the Earth about every ninety minutes. You can expect the ISS to pass directly over Douglasville, on average, about two or three times a week!
Assuming the ISS is overhead, you will need the right radio equipment to communicate with its onboard radio. The ISS Kenwood TM-D710E uses Very High Frequency (VHF) and Ultra High Frequency (UHF)-based communication; this is opposed to the AM/FM frequencies your car radio picks up. VHF/UHF radios are inexpensive and come in many forms (handheld, mobile, and base station). You will need a radio and amplifier with the requisite amount of power if you wish to talk as well as listen; typically, 10W of power is plenty sufficient. Make sure you tune to the identified ISS frequencies: 144.49 on the uplink and 145.80 on the downlink. The uplink frequency is for communication going up to the spacecraft, whereas the downlink frequency is for communication leaving the spacecraft. Having two separate frequencies minimizes the amount of traffic radio operators sending via uplink will hear.
The daily life of an in-space astronaut is thoroughly regimented and chock-full of experiments and spacecraft maintenance. Unfortunately, very little of that involves the Kenwood TM-D710E radio. Astronauts, unsurprisingly, must also sleep, exercise, and eat meals. A typical week on the ISS involves five and half working days and one and a half days off. NASA publishes the daily itineraries of astronauts aboard the ISS; from there, we find that the best windows of opportunity for an astronaut to use the Kenwood radio is either POSTSLEEP or PRESLEEP. Both periods are about an hour and a half in duration, and begin at 6:00AM GMT (2:00AM EST) and 7:30PM GMT (3:30PM EST), respectively. Alternatively, you can try to reach them on their day and a half off. Luck favors the persistent!
The final requirement is a legal one. Given that the ISS is overhead, you have the right radio equipment with the appropriate frequencies tuned in, and have caught the astronauts during their waking and off-hours, you may be able to hear them. Unless you have an amateur radio license from the FCC however, you will be unable to talk back. The FCC requires amateur radio operators to obtain a license to ensure they know enough to minimize radio interference while also operating only on permitted frequencies. There are three levels of licensing — Technician, General, and Amateur Extra. Each requires passing a multiple-choice exam. These exams are administered periodically at local libraries — I took my licensing exams at Dog River Public Library in West Georgia, just last year!
Talking to astronauts over radio is tricky business that requires just the right combination of knowledge, equipment, and sheer luck. The first time your voice rings through the modules of the ISS will make all the hard work worthwhile. Catch you on 144.49!
Mahdi Al-Husseini (call sign KH6AV) is an engineer, a computer scientist, and a medical evacuations helicopter pilot for the US Army.