Dive into the Deep Space Network

This week, MSc student Brittney Cooper examines the Deep Space Network, a key asset for Planetary Science. Above, you can see a screenshot of the live DSN page, on what we now know to be the penultimate planned attempt to contact Opportunity – a tip of the hat to an amazing rover mission and its team. 

by Brittney Cooper

I know I’m quite behind the times with this but I recently stumbled upon the live Deep Space Network (DSN) page called “DSN NOW,” and I’ve been mildly obsessed with it ever since, keeping the page open as a permanent tab in my browser. Getting to see cool things happen in real time definitely is part of the appeal, but my involvement in MSL mission operations has also allowed me to develop a deeper appreciation for this kind of thing… definitely more than I ever had before. 

Being a part of MSL mission planning has you navigating and working around communications passes when satellites orbit overhead the rover, meaning that mission scientists have to manage the data volumes of observations so that necessary data can be down for the next planning day, and the lower priority stuff can trickle down later on.

But what does “trickle down” mean? How does all the data from a rover on Mars, or a satellite headed toward the Sun, get to humans on Earth? I wanted to look into this on a deeper level, after watching a documentary on the Voyager missions called “The Farthest: Voyager In Space.” It left me wanting to learn more about how we are still able to communicate with space probes that are effectively “beyond” our solar system.

The DSN is operated by NASA’s Jet Propulsion Laboratory (JPL) in California, and it is made up of a network of radio telescopes located in Australia, Spain and the United States.  These placements allow for the globe to effectively be divided into thirds, so that constant contact can be maintained with spacecraft. The network has this spacing because radio signals cannot penetrate through the planet, so when Earth’s rotation moves radio antennas at one geographic location out of the line of sight of a spacecraft, it also moves radio antennas at a different geographic location into line of sight of that same spacecraft – constant communication.

The “DSN Now” page shows you which antennas at which location are communicating with which spacecraft, and that in itself is pretty awesome. It also lets you know the spacecraft’s range and the round-trip light time – that is how long it takes for a radio wave to travel the distance to spacecraft, and back. You can also see whether the antenna is sending data to the spacecraft, or receiving or tracking it.

In fact the DSN has a number of functions such as telemetry, spacecraft command, tracking, and science. The telemetry is the downlink from a spacecraft that contains important data products for mission scientists and engineers, which are then processed and distributed by the DSN. The uplink from the DSN to spacecraft is known as “spacecraft command,” which contains the sequences put together by mission engineers, essentially giving a spacecraft its marching orders. Tracking on the other hand requires a bit of give and take, and results in precise measurements of the position and velocity of a spacecraft. Given that the DSN is made up of radio telescopes, the antennas of the DSN can also be used for science such as radio astronomy or radar mapping of solar system objects.

NASA’s 34-meter dish in California is part of the complex of DSN antennas that received Neil Armstrong’s words from the moon. Image: DOUG ELLISON/NASA

Really, the success of the DSN relies on the underlying principle of a game of catch. Both antenna and spacecraft (or a relay spacecraft) need to be in each other’s line of sight, and one needs to be prepared to receive when another is transmitting, and vice versa. It gets tricky to maintain the line of sight portion of the equation when you are dealing with landers and rovers on other planetary surfaces, and stationary telescopes on Earth’s surface. Often in these instances, a relay spacecraft in orbit or doing a fly by near the landed probe/rover will lend a helping hand with the uplink or downlink, and act as a messenger between the two.

It’s really spectacular to think about the logistics required to manage and maintain such an intertwined network made up of various antennae scattered over the globe, and various spacecraft scattered throughout the solar system. Be sure to check out the “DSN Now” page (https://eyes.nasa.gov/dsn/) to take a look for yourself, and if you’re interested to know the location of the spacecraft that the DSN is communicating with, download the “NASA’s Eyes” app (https://eyes.nasa.gov/), from which “DSN Now” is derived – it’s a cool tool to help get better acquainted with both our planet and the rest of the solar system.