How Did NASA Lose a Mars Space Probe Because of Maths?
100 Comments


For all the knowledge of the thousands
of scientists and engineers in the space industry sometimes the old adage of “The best laid plans of mice of men” can be equally applied to their efforts. This
was certainly the case of a Mars climate orbiter mission of 1999 and this will go
down in space history as one of the biggest facepalms to date. If you’re an
avid comment reader then you may have seen comments on my videos about why I
tend to use both Imperial and metric units instead of just metric basically
the simple answer is that many people in the US and the UK still use the Imperial
system even though metric is now the de facto measuring system in the science
and engineering worlds. Now this is fine providing that you don’t get them mixed
up when you’re doing your calculations like the engineers and navigators of
Lockheed Martin and NASA did in 1999. In the late 1990s NASA was under pressure
by the Clinton administration to make each mission go faster, smaller and
cheaper, so rather than focusing on a single large project NASA diversified
their operations this meant that in 1999 whilst servicing
the Hubble Space Telescope and building the International Space Station, NASA
also planned a low-cost program to operate three missions simultaneously on
the Red Planet. The “Mars Surveyor 98” program featured the Mars Polar Lander
with a pair of impact of micro probes on board and a satellite and communications relay which was the Mars climate orbiter. this extraterrestrial probe, it was hoped,
would conduct the first long-term detailed study of Martian weather. Mars
climate orbiter had to be low mass so it was fitted with a single solar panel
rated at 500 watts at Mars. This asymmetrical design meant that the
spacecraft was subjected to rotational force as the panel caught the solar wind,
the probe could correct for this using the onboard reaction wheels but these
needed to be periodically desaturated or reset using corrective burns from its
hydrazine thrusters. These routine maneuvers were recorded in a fire
on Lockheed-Martin’s ground-based computer from which for navigators had
calculated periodic course corrections. However during the nine month trip
regular tiny thruster burns were compounding into a sizeable problem. As
was customary Lockheed Martin’s contract stipulated that all communications
should use the standard metric units, so in daily sensor readings all data was
assumed to be the metric standard of Newton’s of force per second
unfortunately there had been a major oversight the files actually contained
measurements in pounds of force per second using the imperial units which
was still widely used in the launch industry at the time. Because one pound
force equals 4.45 Newton’s force each of the corrective
thruster operations was underestimated by a factor of 4.45,
putting the craft into the wrong trajectory. These showed up when several
navigators at NASA’s Jet Propulsion Laboratory of JPL noticed that something
was amiss. The probe was making more than ten times as many minor adjustments as
planned as it tried to compensate to keep it on course,
however these concerns were never raised formally. On September 23rd 1999 the Mars climate orbiter was scheduled to approach the Martian surface at a
distance of a 140 miles 226 kilometres whilst performing a long
retrograde burn to enter an elliptical orbit around the Red Planet. Just one day
before arrival JPL latest calculations indicated that the probe might be
off-course and could approach Mars at an altitude of just 93 miles or 150
kilometers. The operations team met and discussed the possibility of executing a
contingency burn to raise the trajectory of a probe but with only a day to upload
and carry out this maneuver and some uncertainty about the precise location
of a probe the burn was never executed. Now the team could only hope that the
approach would not be further off course then calculated.
If the probes altitude dipped below 53 miles or 80 kilometres it would burn up
in the atmosphere. Far from Earth, Mars climate orbiter continued its course and
at 9 a.m. UTC began its main engine burn the probe decelerated and passed beyond
the horizon of Mars out of radio contact. 23 minutes later the ground control team
listened for a signal but heard only silence. The Mars climate orbiter was
never heard from or seen again and no wreckage has been found to date but more detailed calculations later indicated that its course fell to just 37 miles or
60 kilometers from the surface, at this altitude there was no way back the
atmospheric friction was far beyond the fragile probes limits and the orbiter
was destroyed. After the incident a report was commissioned which is still
available to download and read which criticized the lack of communications
within NASA and with a contractor Lockheed Martin and the lack of training
for key operatives on the mission. Lockheed Martin and JPL learned from
their mistakes five years later the two organizations together developed the
Mars Reconnaissance Orbiter a mission that accomplished many of the goals of
its ill-fated predecessor using exclusively the international language
of scientific measurement namely the metric system. Now technically the probe
was not lost because of maths but because the calculations were fed the
wrong information, namely good old-fashioned human error. It’s the old
programmer saying of rubbish in rubbish out but when all the data is correct
it’s amazing what can be done with just the power of math. Our modern world and
things like space probes to Mars would just not be possible without someone
doing the calculations. If you’ve ever wondered what it takes to calculate the
route for a Martian probe other guys over at brilliant.org can help you.
Brilliant is an interactive problem-solving website where you get to
learn by solving real-world problems and think like a scientist or astronomist.
There are tons of problem-solving courses on things like gravitational
physics that underpinned a motion of the planets or you can try your hand at
astronomy and do things like finding out the size of the universe and if you’re
into rockets and stuff you can try classical mechanics to work out how
things move around on earth and in space. Sounds like rocket science? well it is
but that doesn’t mean the say has to be hard. Brilliant do this by showing you problems and breaking them down into
easy-to-understand steps then putting them back together so you can see how
the overall process works they also have a large active worldwide community ready
and willing to help you along every step of a way so you’re never alone. To help
support as a curious droid and to learn more about brilliant just click on the
link to brilliant.org/curiousdroid and sign up for free. As a
special bonus for curious droid viewers, the first 200 people to sign up will get
a 20% discount off of their annual subscription.

100 thoughts on “How Did NASA Lose a Mars Space Probe Because of Maths?

  1. The metric confusion reminds me of another aerospace incident, the "Gimli Glider" where an Air Canada 767 ran out of fuel due to imperial/metric confusion. That was in 1983. Fortunately the pilots could fly better than compute and they managed to "dead stick" land the plane in Gimli, Manitoba.

  2. Being in the US It helps me get a better understanding of what metric units are in relation to imperial when you use both. I now can imagine things in meters instead of having to do a conversion in my head from feet. Thanks

  3. Trouble always happens using the metric system, that is why America uses Imperial! Who would you fly with, American Airlines or Air India?

  4. SI unit was agreed by US, but never got around adopting it. In fact all their weights, lengths and other unit of measure conform to metric then they add a ratio factor into imperial.

  5. How does an engineer working on a project like this manage to notice TEN TIMES more course-corrections as expected but never say anything? Lockheed Martin deserved to have egg on its face for this fuckup.

  6. I notice in the new Lost in Space, the dialogue is all in imperial while the ship readouts are all in SI! No wonder those idiots are lost!

  7. Correct me if I'm wrong but if you ionize the burner exhaust gases you can rignaited and prolong the oxidation process prolonging the hydrogen supply

  8. Here’s the short version: Lockheed Martin fucked up and used imperial and nasa thought it was metric while the contract clearly said metric only

  9. When this happened, I just had trouble believing this could happen. ALL of science has been using the metric system for decades. Now that you mention launch systems still using imperial, it kind of makes sense, but I wonder with that conflict how we ever had so much success with all of our other planetary probes.

  10. Your stated reason (metric vs English units) WAS NOT the reason for the navigation failure. It was management failure! First, the craft was "navigation Hell" in that the asymmetrical design and the asymmetrical burns were done. No navigator was on the team when the craft was designed. The wheels could have been desaturated by rotating the craft about the axis to the sun, but management forbid this, along with also forbidding desaturation burns split into 2 done a half-turn apart to cancel translations. Either of these schemes would eliminate the translational cross-coupling with the rotation. Good navigation is best done without any translational burns, so pure inertial calculations can be done. (Also, the statement I heard was that the "correction" for the burns was 4 x, not 1/4th X as you stated). Regarding the last-minute burn, the team knew it was needed, but management denied it to be done.
    You completely fail to explain exactly how navigation is done, and that it becomes more "sensitive" when near a gravitational body. Error was not evident in deep space, but became evident when getting near Mars. Management did not understand this, and chose to "trust" the earlier, less sensitive, measurements.

  11. My dad worked on this project, so every time I would made a small mistake while working on my math homework he would say "You're going to crash your spaceship."

  12. They lost a space probe because of the imperial unit..and you're telling that they missed only by 27 miles.
    How ironic is that.
    Even after losing a million dollar space probe you are still explaining it to is in miles.

  13. Ah, you know what they say about metric, some countries use it and some countries have been to the moon.

  14. The US doesn’t use the imperial system, it uses US Customary Units. There are distinct differences between the two.

  15. well currently OJT as cabin mechanic we use Metric in all our tools cuz there was a disaster when some OJT don't know imperial wrench size example 1/8, 3/2

  16. All right the whole system has to be readjusted to include a category for your Channel. As far as I'm concerned, the best Channel repeatedly and I've never been less than glued to my tablet! Bravo!

  17. We will only change from Imperial when Europeans stop getting all huffed and puffed about it, because until then it's simply too entertaining.
    How is that new Esa Mars Lander doing anyway? Google search… That's an interesting crater. Pretty cool how America used our maths and went to find that crater for you guys lol.

  18. This used to frustrate me to no end when I was a CMM programmer. There's absolutely no reason to ever use the Imperial system in engineering.

  19. I am an American and I find it appalling that my country is to stupid to switch to what is a vastly superior mathematical system. This country has its head so far up its ass that we are now the joke of the world.

  20. we also need to forget about nautical miles and feets on planes. we can use kilometres for everything! simple-smaller-smarter-faster!

  21. This is why going back to the moon is difficult. If a mistake like this can be made imagine now nothing exists anymore (hardware & software) and more important the people with the detailed knowledge have gone. As a programmer you know how easy it is to change and fix code you were the one that wrote, as apposed to if you pick up a totally new code base. Now multiply that by a factor x1000 and you have technology that's all but essentially lost without significant resources and time (even then chances of failure are probably higher than when it was first created). Why I'm talking about the moon IDK 🙂

  22. Curious Droid, I am curious about how pressure or lack of pressure have an impact on metal alloys and composite materials, will they expand same as human body? How spacecrafts manage to not beeing torn apart in space where there is no pressure? Specialy something made from foil like 5:39 mars orbiter probe.

  23. Back in the day, when this happened, my mom was a staffer for the man who was 'The Guy' in charge of this mission…it was His Baby, and the buck stopped with him. I won't mention his name. You can believe the office was gloomy beyond words whenever he was in. He just was beside himself…in shock, zombified. It was a good thing he wasn't too far from retirement, 'cause after the event, his career sort of fizzled. My own boss at the time, was giving me MAJOR crap about it, cracking rude jokes and all that for days, until finally I had enough and told him that, as soon as he can get something to crash into a distant alien world — if he can get ANYTHING even into space, out of the atmosphere never mind to Mars — THEN he can talk all the shit he wants for as long as he wants, and I will listen and take it ……his grin was gone, he muttered something under his breath, and went back into his office.

  24. i absolutely hate math ,with passion im just so happy theres sum heros out there that can haha. Me , Im more of a practical risk taker 😛

    In the uk we still do miles per hour driving, yet i measure everything in mm cm m then when it gets to km i change to miles since i only know the distance of a mile from driving haha.Our fuels pumped in Litres yet the cars show miles per gallon. And i know thers 28G in an Ounce from ermmmmm…drugs…so there not all bad haha

  25. Thank you for using both systems. It's real world from mechanics to rocket science.
    It's funny how a nut/nut can be so picky about the size, but hey, that's life!

  26. Good explanation. Here are a few more facts: the previous mission "Mars Global Surveyor" had TWO symmetric solar arrays which cut WAY down on the number of desaturation burns required. THIS is why Mars 98 had to do ~10X the number of de-sats. The requirement that all data telemetered to the ground WAS followed. These values (with the wrong units) did NOT come down as "telemetered" data but as FILES which did not have to meet that requirement. Next JPL initially yelled at Lockheed for even HAVING the piece of code that calculated the forces in the wrong units. JPL was a little embarrassed to learn that the code in question was provided BY JPL when they delivered the thrusters they wanted used on the mission. Finally during the failure review board at Lockheed, a fist- fight broke out between some of the JPL navigation engineers when the lead stood up in front of everyone and stated "We had NO INDICATION that there was a problem with the trajectory". Apparently a new hire, right out of college, told the JPL Nav veterans that there WAS a problem but they refused to believe "the new guy". Turns out they should have listened to the new guy…

  27. How to waste billions due to stupidity.

    Time for people to drop the old imperial measurements and adopt Metric world wide then such waste of resources and money would be easily avoided.

    I can already hear the screams of those dedicated to the now antiquated and confusing Imperial system of measurements.

    By the way, I'm 69 and going metric was a breeze for me.

  28. Visiting Mars is as much a waste of time and money as trying to revive Obamacare.
    Conquer the Moon because it's doable. Whoever conquers the Moon will rule the Earth.

  29. I have already heard this story but it wasn't that simple. Misreading the instruments for metric rather than imperial would make a difference so big that the probe would end up in Venus rather than Mars. The story that I heard about involves, yes, using both Imperial and Metric system, but the problem was the integrated error of converting to and fro both systems. Something we would just take for granted while programming.

  30. Americans using the metric system leading to disaster? No surprise there. In the DM-1 launch coverage SpaceX used "metric": altitude in kilometers (OK) velocity in km/h (seriously?!) Km/h is a legacy unit, only used for things like cars and airplanes. It's not a standard SI unit. It should have been m/s.

  31. Imperial should be world standard. The units make more sense than European measurements. Everything they do is on the wrong side of the road lol. We invented cars. But some Brit said hey….let's be dicks and make ppl drive on the wrong side and make measurements that piss people off constantly.

  32. Any mention of the fact that the Mars Polar Lander also crashed, except that time, they didn't have the same units conversion problem?
    Didn't think so. No, NASA had months of notice to fix the conversion issue along with a laundry list of other problems they had with both the orbiter and lander. It was the NASA management who refused to accept their contractors' concerns because they emailed management instead of filling out the correct form.

    So no, this wasn't a fiasco because of a single conversion mishap. It was more like because management was more concerned with TPS report cover sheets than with months of problems with the flight of the space crafts.

  33. Imperial or metric I was schooled with both so not a problem. The old chain and rods leaves most in the dark though.

  34. Metric is NOT the defacto system in the engineering world in the US. We still use imperial. Yes, my graduate engineering research was published with both units, bot the work is performed in imperial. Metric is a smarter system. We just don't use it. It is as out dated as our electoral college.

  35. The US does not and never did use the Imperial System, that is a UK/Canadian system. The US uses the US Standard System which is different and based on the English System of measurement which was replaced in the British Empire by the Imperial System way back in 1824. The US was independent long before 1824 and NEVER adopted the Imperial System.

  36. Well, Dan Goldin came from SAIC – the crown jewel of covert technology operations – and managed to have both Observer and Polar Lander fail on his watch. Respectfully, I think there was something else going on and that is why Dan Goldin has been (reliably) quoted as saying "the masses are asses, they don't deserve this information."

  37. These two space agencies are meticulous in their work. I find it hard to believe that something as obvious as the unit conversion was the cause of the craft's destruction– if it indeed it crashed. Both agencies go through a detailed, extensive list of checks and measures that are designed to weed out problems. I think they may have discovered something on Mars that needs to remain classified. I don't buy the unit conversion oversight.

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