Friday, May 16, 2014

Answer: How hard is that comet?

1.  What's the name of the robot probe that's headed to 67P/Churyumov-Gerasimenko, AND what's the name of the landing craft?  (As is traditional, they each have different names.)  
2.  The anchoring device was built by a member of the EU.  Can you figure out what company built the anchoring device?  (And what do they call the device?  As is traditional.. everything has a name... ) 
3.  Suppose we wanted to contact the members of the team who built this device.  Can you find a phone number or email address for them? 
4.  The anchoring device has a built-in g-force instrument to measure how hard the surface of the comet is.  What is the maximum g-force that this device can measure?  Hint:  Find the spec-sheet for the device.  (This one is really extra credit--a little harder than most)   


The name of the spacecraft isn't that hard to discover:  Starting with what we know,  a search for: 


leads to the comet's Wikipedia page. From there it's a simple hop to find that the satellite is the Rosetta mission, being run by the ESA (European Space Agency).  I then did a SITE: search inside of for more information about Rosetta and Philae (the lander).  

     [  Rosetta ]  
Image of Philae landing.  Courtesy

and this spectacular image of Philae landing on the comet.  

2.  To figure out the anchoring system, I did a simple search: 

     [ Rosetta anchor ] 

which took me to the Rosetta press release page at which in turn took me to the MUPUS web page. MUPUS is an acronym for 
Multi-Purpose Sensors for Surface and Subsurface Science.  It's the package of sensors on the Lander's anchor, probe, and exterior to measure the density, thermal and mechanical properties of the surface.

If you read that carefully, you'll see that it's not the anchor itself, but the sensor package ON the anchor.  

The Principal Investigator (PI) for MUPUS is Tilman Spohn at the Institut für Planetenforschung, Deutsches Zentrum für Luft- und Raumfahrt, Berlin, Germany.

We're close, but that's not quite the anchor itself.  So I backed up and did a search for just: 

     [ Philae ] 

and found the Wikipedia page for the Philae lander.  From that page we learn that "The Austrian Space Research Institute developed the lander's anchor and two sensors within MUPUS, which are integrated into the anchor tips. They indicate the temperature variations and the shock acceleration."

That's the nub of the question, and the shock measurement was done by the Austrians!  Once you know that, it's not hard to figure out that the Austrian Space Agency did the work at IWF Graz (Austria).  I then did a search for:  

     [ Austria space MUPUS harpoon ] 

Why did I include the word "harpoon"?  Because I'd seen it used in the ESA press release.
The MUPUS, with PEN and electromagnetic hammer
device incorporated. Note the windup reel at the
back of the device to provide tension once attached
to the body of the comet.  It really is a harpoon.
 I just figured that this was the specialty language they'd used.  (And if this hadn't worked, I would have tried "anchor" next.)  This is a funny terminology issue:  The harpoon device is also called the PEN. The PEN (short for "penetrator") is basically a hollow rod, 35 cm long, which will be deployed at a distance of about 1.5 m from the landing module and inserted into the cometary soil by means of an electromagnetic hammering mechanism.

I found the ESA document about MUPUS, which describes the work as being led by Tilman Spohn (at the Institut, which in English is the  Institute of Planetary Research at DLR Berlin). 

Most of the hardware for MUPUS was built and tested at the Space Research Center of the Polish Academy of Sciences, Warsaw, under the guidance of its present director Dr. Marek Banaszkiewicz.

You can see this is a real cross-European effort.  But who did the pressure probe that's built into the harpoon?  MUPUS is made up of many parts.  Who did the pressure sensor?  

The people most responsible for the pressure sensor system were listed on this MUPUS document:  Günter Kargl and Norbert I. Kömle at the Austrian Space Science Center in Graz.  (Now, with their names and work locations, it's trivial to get their email addresses and phone numbers. I'll leave that to you.)  

We're getting closer:  who built the harpoon itself?

This took a couple of queries, but the one that succeeded for me was 

     [ Philae Kömle harpoon ] 

(Where Kömle is one of the names of the Austrian team doing the pressure sensing package.) 

This search took me to the Philae Lander Fact Sheet, which clarifies everyone's role--who did what, and where. 

In this document you'll find that IWF did the design and performance testing, while MPE Garching built the hardware. (This is the Max Planck Institute, near Munich.)  In particular, IWF chose the accelerometer and temperature sensors for the probe.  Handily, they even specify the particular sensor model numbers!  "ANC-M is a shock accelerometer (ENDEVCO 2255B-1).  The attached conditioning electronics allows this sensor to measure a decceleration history with a frequency of 33kHz.  Decelerations up to 12,000 g can be measured with special conditioning of the sensor signal."  It goes on to say that "Engineering models for the comet surface properties covered a range for the compressive strength between 60 kPa and 2 MPa. The surface roughness is completely unknown. Extreme surface compressive strengths down to a few kPa are now covered as well."  

"kPa" and "MPa" are kilo-Pascals and mega-Pascals (units of pressure).    

I know that all parts (like sensors) have datasheets for them.  So a quick search for: 

     [ ENDEVCO 2255B-1 datasheet ] 

took me to the maker's datasheet for the device.  It turns out that it was actually manufactured just down the road from the Googleplex in Sunnyvale, CA!

If you read this datasheet carefully, it looks like the Austrians figured out a way to clean up ("condition") the signal to get slight better performance than the manufacturer says is possible.  Excellent!  

Search Lessons:  There are several here.  

1.  I used SITE: to restrict my searches to just within ESA.  That's obviously not required (lots of people figured it out without this operator), but it's frequently a good tool for just this purpose.  (Searching with a single site.) 

2.  Using an investigator's name (Kömle) is often a great way to zero in on a topic.  Scientists tend to write papers on their topic of interest, and if you get a rare name like this, it's usually a fast way to zero in on info.  

3.  Sometimes you have to play around with speciality terms.  In this example, "anchor" and "harpoon" were good descriptions of the device we were searching for.  Sometimes one would work, sometimes the other.  It's still research after all! 

Search on! 

You can find out more about the Rosetta landing and anchoring system at this paper:  "The Rosetta Lander ("Philae") Investigations."  

1 comment:

  1. You used the term recently "deep answer" and this is a great example. Part number is a great query [I should have known being involved in the automotive industry].Query[ kpa mpa ] would have helped with terminology. As well datasheet vs spec. sheet opened up an entire new avenue. So many little details but important to get the deep answer. But even more so was learning about the Rosetta Mission. Very interesting challenge.