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Any opinions, findings, conclusions, or recommendations expressed in this material are those of the developer, PASSPORT TO KNOWLEDGE, and do not necessarily reflect those of the National Science Foundation.


  Michael H. Sims
  MER Co-investigator
  Center for Mars Exploration
  NASA Ames Research Center

Mike's MER Journal: Sol 3 "Fatigue" (Sol 3 is ~January 5, 2003)


This Journal contains informal and spontaneous comments by Mars Exploration Rover science team member Mike Sims, normally based at NASA's Ames Research Center. Mike writes: "There is nothing official, approved or necessarily even 100% accurate about my ramblings. My intention in this is to share as honestly as I can a bit of the flavor of what it is like to work on a NASA mission at the scale of a single human being and to convey something about what we are up to. My intention is that if I (and you!) make it through these Journals, you will know great deal more about Mars and what we are up to with MER. My hope is to convey a lot of information and make it accessible to even the youngest of readers." Thanks, Mike, for agreeing to allow P2K to post your thoughts online!

Today ramblings:

Steve Squyres (our fearless leader), Jim Bell (the PanCam Camera lead) and the whole Pancam team (with support of the rest of the MER team) has given us a truly wonderful picture of Mars! Check it out at It's worth at least a thousand words, so for the moment I'll let it speak for itself.

When I arrived at "Science Ops" (our shorthand for operations) yesterday I felt tired; I felt tired when I went to bed at 4 a.m. this morning; and I was also felt tired when I awoke later at 10 a.m. I'm a "7 to 8 hours of sleep" sort of guy. I need to make sure I get my nap today. That would be just a boring footnote in anyone's life and of little interest except that a couple of unusual things are going on. First, the MER mission is an exciting time and to us it's a big deal (!). It is scientifically interesting to understand how people manage in times like this of high excitement and high stress. Understanding this better might have all kinds of applications. Maybe it could impact how firefighters work, or how a mission control team watches over astronauts' safety, for example.

The second interesting element of fatigue relevant to MER is that we are working on a "Mars day" schedule rather than an "Earth day" schedule. Mars spins on its axis slightly slower than Earth spins on its axis, so the day on Mars is longer by about 40 minutes. So, if we want to have a Mars robot (say the Spirit robot sitting in Gusev Crater, to pick a completely random example!) wake up at 10 am every morning then we would have it do so at what amounts to roughly 40 minutes later each day from the perspective of Earth. To distinguish a Mars day from an Earth day we call a Mars day a "sol" which I believe is short for "solar return." In other words it takes the Sun on Mars roughly 40 minutes longer each day to return. Just as on Earth, however, the length of daylight varies over the year.

It turns out that we do want the rover to do things at roughly the same time each Mars day. One reason is that Spirit is a solar powered rover and, like on Earth, we get the best power when the Sun is high in the sky and less as we get closer to darkness. So the Mars equivalent of high noon is a great time to do things from the point of view of Spirit's power. A second reason we like to do things on Mars time is that much of what we do with a rover is taking images (see item 1 above!) and the time to do that is during the day.

Keeping track of what time it is on Mars is essential for our team. (Ed. note: you can see what time it is on Mars by downloading the Mars Clock application from NASA's Goddard Space Science Institute site at: In addition, we have chosen to uplink one set of commands to the rover per sol. There are exceptions to this, but from the science perspective this is largely how we work. So, what this seems to lead to is the conclusion that it is more efficient if the team also operates on Mars time. But that means I should go to bed, get up, eat meals, exercise, talk to our family, read email and all that 40 minutes later each day.

Studies dating back to the 1950s of people placed in caves without exposure to sunlight and clocks showed that humans can usually adjust to slightly longer or shorter days. Individuals have a natural day length rhythm that varies from person to person. This natural rhythm is encouraged into a day-night/awake-sleep cycle by a hormonal response of our bodies to external stimuli, most importantly bright sunlight. So in principle we can force our bodies into these slightly longer days, especially if we are can adjust our exposure to bright lights appropriately. The MER mission decided to shift the whole team to a Mars day cycle. As you can imagine most of the world around us isn't particularly supportive of this type of time rhythm. In my mind, the jury is still out as to whether this was the best choice or not. I found it interesting that the late Jim Martin, the leader of the Mars Viking teams in the 1970s, chose not use Mars time for Viking after a short initial period, and recommended against our using it in MER. Our circumstances are somewhat different, but I believe there are good arguments for both using Mars schedule for the large team, and not using it. Be that as it may, we decided to set our clocks to Mars time, and everyone's daily cycles are easing forward 40 minutes per day.

Actually, the game is considerably more complicated than simply the 40 minutes additional each day. I'll speak only of the science team issues but there are similar issues for the entire "ops" (our patois for operations) team. There is one science team for both MER rovers, Spirit and Opportunity. We are a large team (maybe 100-150 people depending on who you count) but in my opinion we are maybe half the size of what would be a comfortable number of people. (I don't intend this to be critical of any past decisions rather to be an input into choices in the future. For MER by the time we really understood the complexity of the operations it was too late to change this number in a substantive way.) I'm clear that under Steve Squyres' leadership we'll get it all done and do a great job, but it is going to require many people working extremely hard and long hours for months.

Starting the 24th of January well have two rover on Mars, if all goes well. The Opportunity rover will be half a planet away from Spirit so the day-night cycle will be roughly half a day different than that of Spirit. In order to cover the needed tasks for each rover one can think in terms of dividing the team in half. Each rover has a set of absolutely mandatory science team jobs that need to be covered each day. A dozen or so people are required to perform these mandatory tasks. In addition, each instrument needs a team to monitor that instrument and produce instrument products. Those teams may vary from a couple of people to maybe a dozen for the Pancam instrument.

And of course, we need to actually understand the science. That's the charter for the five Science Theme Groups (STGs): Geology, Geochemistry, Soils and Physical Properties, Atmospheres, and Long Term Planning. For each of the Science Theme Groups to be effective they will need at least three people and are better off with half a dozen to a dozen.

In addition, we have two shifts per sol for the instrument teams. One shift focuses on getting the data down, evaluating the instrument, and getting data products built for scientific evaluation. Examples of data products would be for the Pancam camera team to mosaic several images together or form a new color image from three images taken with different filters.

The second shift per sol is the team that builds the commands to uplink to the rovers to control it the following day. In collaboration with the drivers of the rover the instrument teams are responsible for building the commands for each instrument each day. For each instrument there is a particular person responsible for the uplink shift and downlink shift activities. Those individuals are called the Payload Downlink Lead (PDL) and the Payload Uplink Lead (PUL). In addition to being a member of Science Team Groups I work sometimes as the Microscopic Imager's PDL and PUL.

The point of this digression into discussing jobs is to point out that more or less the same set of people are involved in all of these tasks. That's as it should be but that makes it difficult sometimes. These jobs have responsibilities and start times that are all over the clock. And if they aren't all over the clock now just wait a few days and they will be!!! As an individual is needed on the other rover, or on uplink or downlink, the work hours will vary widely. It is also an extremely complicated task to schedule all of these folks. The primary jobs are scheduled and strict rules are applied to make sure people have sufficient chance to rest and time off. At the same time many of us are away from home and families and only occasionally get back or even have a chance to talk. At the very least you can think of all of this as breaking up the old 9 to 5 routine!

Don't get me wrong -there's nothing else I'd rather be doing. We all think of this as a great privilege to have this chance to play with these toys (OK, Steve, serious scientific tools!) on Mars! I just wanted to share a little bit of the flavor of process that you might not find on the 6 o'clock News.

And I should underscore that Steve Squyres (MER principal scientist), Pete Theisinger (MER Project Manager) and JPL take the issue of fatigue very seriously. They have brought in the Ames Fatigue Management and Human Factors teams to guide the countermeasures and to sculpt the processes to best support the teams. There are presentations on the issue, cots all around the offices where the mission and science team operate, blackout windows and support all about. There is a strong commitment by MER to doing what is necessary to make it work for the teams and for the mission.

I'm still feeling tired though! So, for now I'm going to now get out and try to get at least one good meal for the day!

Coming up!
One of the most important things one does with a rover is figure out where you are. Until we have that figured out on Mars we really don't know which direction of the compass we want to head in. At the moment we have a rough idea of where we are, but we don't yet understand it well enough to know which way to go. Once we know where we are then we'll almost immediately know which direction we want to go in. Actually, there are maybe half a dozen groups of people that seem to know where we are. The problem is they don't agree! More on this tomorrow.

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