After reading my Earth Day 2021 post you might be wondering how on “Earth” NASA keeps track of all the probes way out there in space. We know that boats, cars, and airplanes need constant course corrections. So, how is this done with deep space probes and landers? It all happens at Cal Tech’s Jet Propulsion Laboratory in Southern California where I had the opportunity to visit in 1986. I was there just as the very first close-up images of Halley’s Comet (see the video here) taken by the deep space probe, Giotto, were being displayed on the internal monitors. Those images would later be enhanced before sending them out to the media.
After that, our guide met our group and showed us around the facility’s technical equipment, including the Deep Space Network’s (DSN) mission control room, shown above. Looking much like an air traffic control radar room, it’s here the controllers monitor the probes, not with radar but with radio communications. Just as with all the manned spaceflight missions, they use the three antenna stations located at Goldstone, Southern California; Madrid, Spain; and Canberra, Australia. Together, these enable constant communication with the probes as the Earth rotates.
Communication is a bit tricky since commands have to be issued well ahead of time, depending on how far out the probe is. At the time of this writing a round trip signal to Voyager 2, now located outside our solar system, takes 1.47 days. Consequently, commands have to be timed within micro (or nano?) seconds so any course course corrections don’t send the probe off its intended path. This is done with computers since they are much better than humans at dealing with microseconds or less. There is, however, a digital atomic clock (based on the radioactive decay rate of Cesium) on the wall for human reference. It has an accuracy of +/- 1 second every 3 billion years, so you don’t have to reset it too often.
If you would like to check out the current communications state of the DSN (including those with Perseverance), updated every 5 seconds, click here. You can also see the video landing of Perseverance on Mars here.
During this time of declining trust of science and increasing acceptance of superstition and unsubstantiated beliefs, Carl Sagan’s Baloney Detection Kit might help you discern what’s possibly real.