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Working on Mars Time

April 14, 2021

Have you ever wondered what it's like to participate in a rover mission? Read more below!

I work as a contractor for the USGS Astrogeology Science Center as a Payload Science Lead for the Mastcam-Z cameras on the Perseverance rover. As Payload Science Lead, I am involved in the daily operations of Perseverance doing such tasks as evaluating and processing the image data we receive from the Mastcam-Z cameras, and helping to plan the details of upcoming observations for Mastcam-Z. Currently, the entire operations team (a large group of engineers and scientists) are working on Mars time to provide instructions and review data to carry out the Mars 2020 mission goals.

What does working on Mars time even mean? Well, to start you need to know that a Mars day, also known as a sol, is 24 hours and 39 minutes long, just longer than an Earth day. Then, you must appreciate that the spacecraft we send to investigate the Martian surface mostly work during the Martian daytime so that we can image our surroundings and document our science. So it follows that the team of scientists and engineers responsible for day to day operations of these spacecraft are delivering their commands on a cycle that is in sync with the Martian sol rather than the Earth day.


Olivia E. Butler Landing Site Mosaic
Sol 003 Mastcam-Z Olivia E. Butler Landing Site Mosaic (Z-34). Photo Credit: NASA/JPL-Caltech/ASU/MSSS 

It works like this: During the Martian night, the operations team on Earth uses the latest information from Perseverance (location, new images, health and safety information) to make plans for the following sol. Is the rover where we expected it to be? Do we need to move to reach an interesting target? What images or measurements do we plan to take? Once we understand the current state of the rover and the intentions for the following sol, the operations team works the rest of the Martian night to generate the instructions for the following sol. And there is a hard deadline for this process! This package of instructions (a set of commands and sequences) we create for each sol, what we call the uplink, must be ready for the scheduled communication window with Perseverance the following Martian morning. You see, the rover already has instructions about when to wake up and listen for commands from Earth, and we have to be prepared to send those commands on time – on Mars. Once those commands have been sent, the operations team on Earth is done for the “day,” and can get some rest. Perseverance will carry out those instructions and at scheduled times throughout the Martian afternoon and evening will relay data back to Earth through orbiting spacecraft. The Earth-based operations team will get back to work sometime in the Martian evening to start reviewing that data, what we call the downlink, and start the planning process all over again for the next sol.

Let’s revisit an important detail that makes working on Mars time so challenging for Earthlings. As I mentioned, we must have those commands ready by a certain time each sol when Perseverance is awake and awaiting commands. Let’s say for purposes of example that time is 08:00 Mars time, which means the operations team started around 16:00 the sol before (yestersol as we like to say) to receive the latest downlink data. The team spent the Martian evening and overnight assessing the data and making plans that will be ready to uplink at 0800. The thing is, starting at 16:00 every Martian sol does not correspond to a consistent time on Earth for the operations team. That time on Earth is going to move by 39 minutes each day because of the difference in length of day and sol between Earth and Mars. If we earthlings on the operations team start at 16:00 today, we will start at 16:39 tomorrow and 17:18 the next day and so on. Of course, we round those times and add in some margin, but never-the less our start times on Earth just march around the clock like that every day. As I write this, I am preparing for a shift that starts at 16:30 earth-time and looking into next week my shifts will start at 20:00 earth time. 

This is my second experience working Mars time. I did it 17 years ago when the rovers Spirit and Opportunity landed on Mars in January 2004. I was much younger and single, and the lack of any other commitments made it much easier. It was great fun and a unique shared experience with colleagues that created memories to last a lifetime. We would get off work at 7:00 in the morning and head to the Santa Anita racetrack to watch morning workouts and wind-down together. We would grab dinner after getting off at 2:00 in the morning at some all-night diner. Nagin Cox has given an excellent TED talk about Mars time that I encourage everyone to watch if you haven’t seen it. Nagin Cox: What time is it on Mars? | TED Talk This time around. This time, I find Mars time just as exciting, and while I miss the camaraderie of working with friends and colleagues, I’m making new memories with my family. I know my kids will remember this and talk about it their whole lives, and that is very special to me.

Working from home during the pandemic.
Alicia Vaughan working from home during the pandemic.


Needless to say, working Mars time is hard on humans and that’s why we don’t do it forever. Most of us are working from home because of the global pandemic and many of us have families. My whole family is along for the ride. We hung black out curtains in my bedroom so I can better sleep during the day when necessary. We must make arrangements as a family to cover when Mom is unavailable either because I’m on shift or I am sleeping at odd hours. Luckily, they all think it’s pretty great and have been really supportive and helpful. Aside from my family, I have to remember to take care of personal things while living on Mars time too. I still need to exercise, get groceries, pay bills, run occasional errands, etc.  I find those things to be the most challenging. I easily get wrapped up in Mars time and the excitement of seeing new data from Perseverance each day. Even when I am not scheduled on shift, I cannot just flip a switch and get my body back on Earth time. I still want to look at the latest data and listen to the science discussions and it takes several days to transition to a normal Earth schedule, especially when I have been working overnight on Earth, completely opposite of my usual Earth-time operation. Because of these challenges, the operations team will probably only keep this up for a few months, and then we transition to rover operations on Earth time. 

You may be asking yourself, if you can do operations on Earth time, why bother with Mars time at all? And the answer is that working on Mars time allows us to be most reactive to the latest data from the rover. When we work Mars time, we are using the most recent information to make plans for the next sol, allowing us to be most efficient with our limited number of sols in the mission. It is very helpful to work Mars time in the beginning of the mission as we work through commissioning activities – getting the payload ready for regular operations. We have to work through all capabilities for the first time on Mars, in the Martian environment, to characterize and calibrate all the instruments. The Mars 2020 mission also has to deploy the helicopter, Ingenuity, and devote a month or so to testing powered flight in the Martian atmosphere for the first time. We will leave it behind and move on with the rest of the mission goals exploring the Jezero Delta and collecting samples. It’s much better to work Mars time through this phase and move as quickly as possible to the main goals and tasks of the mission.


Ingenuity Helicopter
Sol 045 Mastcam-Z Mosaic (Z-110) of Ingenuity Helicopter.  Photo Credit: NASA/JPL-Caltech/ASU/MSSS

Once we transition to Earth time, there will often be sols that are restricted in terms of what we are able to schedule because we are planning without the most recent data from the rover. Ultimately that’s a trade we are willing to make since working Mars time is unsustainable for earthlings. We are still able to plan excellent observations providing high scientific value on restricted sols. And now it’s time to go and look at the latest downlink and make plans for the next sol in Perseverance’s great mission.


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