Terrain-Relative Navigation

It’s Almost Time.


I have already explained the latest Mars Perseverance Rover project in detail. I showed you how it was built, how it got its cool name and where it is going. The landing is scheduled for February 18th. There is one thing, however, that I did not explain and that is how its landing will be different from any other landing of a vehicle in space.

Armageddon Movie
Armageddon- A mission to save Earth from a planet killing asteroid | Movie Poster

If you remember the movie “Armageddon” starring Bruce Willis the scene where they are landing on the asteroid points out why landing in the planned landing zone (LZ) is very crucial to a successful mission. In the movie they miss the LZ and land on an iron plate which causes serious problems.

Perseverance is set to land in the Jerezo Crater on mars. The terrain is very rough and was chosen because of the types of samples they plan to collect and test with the high tech equipment that the rover will use to drill into the Martian surface.

Mars Rover Landing Technique | Photo by JPL-Caltech

What will help Perseverance land is the lander vision system (LVS) that has been rigorously tested here on earth. The Jet Propulsion Laboratory (JPL) at the California Institute of Technology (Cal-Tech) website quotes Andrew Johnson, principal robotics systems engineer at JPL: “Jezero is 28 miles wide, but within that expanse there are a lot of potential hazards the rover could encounter: hills, rock fields, the walls of the crater itself, to name just a few. So if you land on one of those hazards, it could be catastrophic to the whole mission.”

The technology that will help Perseverance make a safe landing is called Terrain-Relative Navigation (TRN) and it will capture pictures of the Mars terrain in real time and compare them to maps already in it’s database. It will then autonomously make the course corrections needed to divert around known hazards and obstacles as needed.

On Launchpad For Test | Photo by Masten Space Systems

This will be the first time the TRN has been used in space, but tests were performed as far back as in 2014 using Masten’s Xombie VTVL system for a test flight to prove that the LVS could make the kind of critical adjustments needed to make the safe landing at the Jezero Crater. According to Andrew Johnson “For Mars 2020, LVS will use the position information to figure out where the rover is relative to safe spots between those hazards.” The system can determine Perseverance’s position relative to to the ground with the accuracy of about 200 feet or less.

According to JPL’s Swati Mohan, guidance, navigation, and control operations lead for Mars 2020 “We have what we call the trifecta of testing.” We’re getting closer to this historic landing on Mars and the hope is that Perseverance will land safely in just the right location and successfully collect samples of Martian debris and soil so that we can learn more about the planet’s past which might help us understand our own Earth’s beginnings.

I plan on updating the rover project once it has landed on Mars.

Let me know what you would like me to talk about or explain. You can comment below or email me at: [email protected].