NASA Phoenix Mission Ready For Mars Landing

Several readers relayed the press release from JPL about the upcoming landing of NASA's Phoenix Mars Lander on May 25. It's going to set down in the north polar regions and look for indications of whether conditions have ever been favorable for microbial life. "Phoenix will enter the top of the Martian atmosphere at almost 21,000 kilometers per hour... In seven minutes, the spacecraft must complete a challenging sequence of events to slow to about 8 kilometers per hour... before its three legs reach the ground. Confirmation of the landing could come as early as 7:53 p.m. EDT. 'This is not a trip to grandma's house. Putting a spacecraft safely on Mars is hard and risky,' said Ed Weiler, associate administrator for NASA's Science Mission Directorate. 'Internationally, fewer than half the attempts have succeeded.'"

Comments

Slow to about 8 kilometers per hour.

[Thanshin]

In seven minutes, the spacecraft must complete a challenging sequence of events to slow to about 8 kilometers per hour... Why reducing the box? Is there any reason to discard a higher speed landing?

What if they find a way of slowing down to 16kmh, they abandon the mission?

I'm not talking about considering compressing time continuum to extend those 7 minutes, but it seems there are possibilities that could still be considered, like hardening the legs, finding a softer spot to land, finding a lower landing spot to extend braking time, etc.

Re:Slow to about 8 kilometers per hour.

[ledow]

Because even at 8km/h you can do serious damage. Any lander has to be extremely light for takeoff from Earth and the transit to Mars, contain extremely fragile equipment, and end up there in one piece. "Bouncing" off Mars is not an option. That requires heavy, expensive materials, or some sort of complicated landed shield arrangement (e.g. giant inflatable bubble) that all add years of work and millions to the cost of the project. You could literally double or treble the cost of the entire project by "beefing up" the lander.

Plus, it has to land under autonomous control, so you really have no idea how fast it actually landed or exactly where until several minutes after it has landed - so coming in a little too fast isn't a good option, neither is a stray patch of rock (there are few "soft spots" on Mars, by the way - it's mostly rock). Much better to land as gently as you can manage and do your braking manoevures in the "air" as you come down. You've got plenty of time, the physics are easier to calculate, and there's less to go wrong.

The first few hours of a new lander's life on another planet are basically checking that everything still works, even with all the gentle landings in the world, things get broken that cost MILLIONS to put them up there. 50% of the things still never make it to the planet operational, even with all the good will in the world behind it. You want to spend MULTIPLES of the cost of the entire project on making the landings more difficult, more violent and less reliable when we can't even get half of what we send onto the planet successfully?

Re: Hard and Risky???

[Anonymous Coward]

It's always hard and risky, even the 10th time you do it. Mostly because each success raises the bar for the next mission. First you land a shoebox sized rover, then a golf cart, then something the size of a Mini. Those are orders of magnitude more difficult in turn.

Paid quite well? JPL pays slightly under industry wages, but it IS a nice place to work, and glamorous. NASA pays substantially lower (government civil service jobs.. but there are some intangible benefits that are hard to quantify, and some that are)

People do get fired for making mistakes.

It wasn't JPL or NASA who supplied the data in pounds instead of the contractually required Newtons. JPL has been metric for decades.

Slow transfer rate to Mars

[cculianu]

From the media kit PDF about Phoenix:

The helical antenna and a monopole UHF antenna, also mounted on the deck, will be used for relayt elecommunications during the months of operation after landing. The lander can send data at rates of 8,000 bits per second, 32,000 bits per second or 128,000 bits per second.

Wow, that isn't a fast transfer rate. That's about 1KB/s, 4KB/s, and 16KB/s, respectively. I guess you don't need too much more -- but still, I bet it's slower than they would like. The high resolution camera alone probably produces images that are a few megabytes in size. Let's say the images are like 4MB -- Transferring 4 MB at 1KB/s takes about an hour!

Given the slow xfer speeds and limited hardware they probably use -- I think it would be fun to be a programmer for NASA. That's one of the few applications where efficiency of communications, small memory footprint and efficient CPU usage probably still count for something.. I bet you everything they do when it comes to the software running on the lander tries to be as efficient as possible (especially communications-wise).

Also, isn't there something like an few minutes of latency for light to reach us from Mars? You can't even really do any really realtime interaction with the onboard computer on the Phoenix lander.. Imagine typing into a shell and waiting a minute for your characters to appear! Ouch! So I bet you they have to premeditate a lot of the changes they make to the software or operating environment way a head of time -- they probably just upload scripts of commands when updating the software or filesystem, etc.

I wonder how much freedom they give the people communicating with the lander. Do they triple-check every command sent to it to make sure noone does the inadvertent 'rm -fr /'?

Re:Slow transfer rate to Mars

[silverpig]

"Also, isn't there something like an few minutes of latency for light to reach us from Mars? You can't even really do any really realtime interaction with the onboard computer on the Phoenix lander.. Imagine typing into a shell and waiting a minute for your characters to appear! Ouch! So I bet you they have to premeditate a lot of the changes they make to the software or operating environment way a head of time -- they probably just upload scripts of commands when updating the software or filesystem, etc." Yes the lag time is several minutes, depending on the relative positions of the Earth and Mars. For the mars rovers the task is quite interesting. Imagine trying to control a remote controlled car around an obstacle course where you have to wait 20 minutes to see the results of your actions. NASA wrote software for the rovers which makes the process largely automatic. They tell the rover to go to a certain place, and the rover has software which basically figures out the best way to get there.

Re:Slow transfer rate to Mars

[ChrisA90278]

The typically have a model of the spacecraft in the lab. any change to the software gets uploaded and tested in the lab. There will be quite a bit of formal testing using a detailed written test plan. Then there is some kind of a change review bord that meets and reviewis the tests and the plan. Finally the changes get packaged up. The they test the upload procedure on the lab simulator. Then finaly the change is uploaded.

Typing into a shell is not only slow but far to risky. Everything gets tested for a good long time and many eyes look it over

It you are the kind of programmer that like just hacking away and changing code until it work this kind of work is not for you. These guys will write up a design and defend it to a review group then they do the code and then they will do a line by line walk through then they go to test. the process is very slow going and productivity runs at well under 200 lines of code per month per engineeer.

Re:Good article and GREAT PICTURES of the Phoenix

[evanbd]

The Mars Scorecard.

Mars currently leads, 20:19, though Earth is making a strong showing this decade.