Rosetta: OSIRIS’ first light!

March 27, 2014

Already taken on the, 20th and 21st of March, I wonder what took them so long to release it although I kept asking them every other day :-)

And here’s the press release: http://www.esa.int/Our_Activities/Space_Science/Rosetta/Rosetta_sets_sights_on_destination_comet


All eyes on #Rosetta part 6: #MIDAS

March 27, 2014

Hey, this is an easy one: ESA actually wrote a detailed description of MIDAS so today I can concentrate on another system :-)

Read more on ESA’s Rosetta Blog:

http://blogs.esa.int/rosetta/2014/03/26/introducing-midas-rosettas-micro-imaging-dust-analysis-system/


All eyes on #Rosetta part 5: #ROSINA and #COSIMA

March 26, 2014

Note: In this – hopefully – daily series of postings I’ll highlight one of the many instruments on board of the Rosetta spacecraft and the Philae lander.

Hello Space Geeks, I’m currently preparing my trip to the DLR in Cologne this Friday (my accreditation was confirmed), so I missed a posting yesterday. Also there’s a family and a day job to take care of! :-)

Today I’d like to talk about the two mass spectrometers on board of the Rosetta spacecraft, ROSINA and COSIMA. First I hand over to ESA what they have to say about these instruments:

ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) contains two sensors which will determine the composition of the comet’s atmosphere and ionosphere, the velocities of electrified gas particles, and reactions in which they take part. It will also investigate possible asteroid outgassing.

Principal Investigator: Kathrin Altwegg, Universität Bern, Switzerland.

http://www.esa.int/Our_Activities/Space_Science/Rosetta/ROSINA

COSIMA (Cometary Secondary Ion Mass Analyser) will analyse the characteristics of dust grains emitted by the comet, including their composition and whether they are organic or inorganic.

http://www.esa.int/Our_Activities/Space_Science/Rosetta/COSIMA

So ROSINA will investigate gases, where COSIMA will investigate dust; but going to to the technology, they pretty much work the same.

ROSINA

The Rosetta Orbiter Spectrometer for Ion and Neutral Analysis; ESA; Source: http://www.esa.int/spaceinimages/Images/2002/11/The_Rosetta_Orbiter_Spectrometer_for_Ion_and_Neutral_Analysis

COSINA

The Cometary Secondary Ion Mass [spectrometer]; ESA; Source: http://www.esa.int/spaceinimages/Images/2002/11/The_Cometary_Secondary_Ion_Mass


What is a mass spectrometer? If you’ve read my posting about ALICE, the ultraviolet spectrometer, you already learned that lights of different colors get “bend” differently in a prism – the prism “sorts” the different colors by their wavelengths and projects it to a digital camera. There we record which colors occur and how bright each color is. We also learned that from the color-composition we can learn from what stuff is made of.

A mass spectrometer uses a similar principle; it takes a sample of gas, sorts the different substances by their weight (instead of color), and counts how much particles (instead of photons) of each mass hit a detector.

So how do you separate atoms by their mass? I’ll give you a a simplified explanation. You use a magnet! First we have to ionize the sample so that it’s electrically charged. What you do is you fire negatively charged electrons at the (neutral) atoms. The electrons hit the atoms at high speed, kicking out the electrons orbiting the atom: Having lost their electrons, only the atoms’s nucleus remains. Since the nucleus only consists of neutrons (having no charge) and protons (being positively charged), the atomic nucleus is now positively charged. Now you accelerate the positively charged atoms (now called ions) in an electric field up to a velocity of few kilometers per second. Now the magic happens: This beam of ions is forced into a curve by another electric field and through a magnet. Since heavier objects in a curve are “lazier”, they don’t take the curve as sharp as lighter objects. A mass spectrometer does exactly this; if the beam of ions is put into, let’s say, a right curve, the heavier ions will arrive more to left after the curve, the lighter ions more to the right. All these ions, now sorted by their mass, hit the detector in different places. The detector counts how much of each at which position arrived and then shows you of what the gas is made of!

This video shows us a lab-grade mass spectrometer as used on earth and explains the principle of operation.

Obviously ROSINA and COSINA are much smaller and less heavier than lab-equipment on earth; after all, lifting a kilogram of material into space onboard of an Ariane 5 costs around 15,000 Dollars, so smaller is better :-) (120 Mio, USD / 6,700 kg payload; Rosetta had a launch mass of 3,000 kg but the Ariane 5G had a unique configuration, so these number may be way too small; I couldn’t find proper numbers, but let’s forget about the money for now:)

Rosetta will send the results back to earth and scientist will analyze graphs like this:

Massenspektrum Tetrachlordibenzofuran

Massenspektrum Tetrachlordibenzofuran; by Wikipedia user chris; License GFDL >= 1.2, CC-BY-SA-3.0-migrated; Source http://commons.wikimedia.org/wiki/File:Massenspektrum_Tetrachlordibenzofuran.svg

And  this is exactly what ROSINA does.

But… how does COSINA then analyze dust? Dust is much bigger than singular atoms or molecules from a gas. It’s easy: Heat it up and vaporize it! COSINA includes a little oven, where dust samples are heated up and brought into the vapor-phase. And then it’s pretty much the same as with ROSINA; ionize, accelerate, bend around a curve, shove the ion-beam through a magnet to amplify the seperation and let them fellow bang into a detector. Count hits, create spectrum, send to earth. Voila!

And that’s how you figure out what gases and dust is made of; on earth and in outer space.


400,000 Stars | The Memory Palace

March 25, 2014

A touchy short podcast about Edward Pickering’s staff of human computers.

http://thememorypalace.us/2014/03/400000-stars/


Nice SOFIA video on YouTube

March 25, 2014

Inside NASA’s SOFIA Airborne Astronomical Observatory:

“They can see SOFIA operating [...] the next 10 to 15 years” – unfortunately NASA cut the funds so that operation will cease by September if no solution is found! Operation costs is about 85 Million USD and only 9 Million USD by DLR are left. Please. Get funding. Try to find a solution. Go and talk to ESA – Roskosmos – JAXA – whatever it takes.


All eyes on #Rosetta part 4: #CONSERT

March 24, 2014

Note: In this – hopefully – daily series of postings I’ll highlight one of the many instruments on board of the Rosetta spacecraft and the Philae lander.

Hello Space Geeks, welcome to the fourth posting of this series about the scientific instruments on board of Rosetta and Philae! It’s Monday and only four more days to go until the DLR will host it’s big recommissioning-event in Cologne, and boy, am I excited.

Today I’d like to present you CONSERT, the “Comet Nucleus Sounding Experiment by Radio wave Transmission”-experiment. This experiment consists of two parts, first a transmitter on board of Rosetta, and a transponder installed on the lander Philae. CONSERT was built in cooperation of the Max-Planck-Institute for Solar System Research and the l’Institut de Planétologie et d’Astrophysique de Grenoble.

CONSERT (Comet Nucleus Sounding Experiment by Radiowave Transmission) probes the internal structure of the nucleus. Radio waves from the CONSERT experiment on the orbiter travel through the nucleus and are returned by a transponder on the lander.

Principal Investigator: Wlodek Kofman, Institut de Planétologie et d’Astrophysique de Grenoble, Grenoble, France.

(Source: http://www.esa.int/Our_Activities/Space_Science/Rosetta/CONSERT2)

Basically CONSERT works as follows: After Philae landed on 67P, Rosetta will fly around the comet until it’s facing the opposing site. Now, CONSERT’s trasmitter will send a 90 MHz Radar-signal right at the comet and Philae’s transponder – sitting on the other side of the comet – will try to pick up the signal, modify the signal by some data (that’s what a transponder does) – and send it right back, through the comet again, to Rosetta.

Transponder Operation Principle

Transponder Operation Principle; Waveform 11 shows what Rosetta initially sends out, Waveform 12 shows the data Philae want’s to encode (time of receive, signal strength, phase-, frequencies-shifts if any), Waveform 13 shows the modulated transponder signal Philae sends to Rosetta; From US Patent “Radar transponder operation with compensation for distortion due to amplitude modulation”; Source http://www.google.co.in/patents/US7864097

Rosetta then will pick up the modified (“modulated”) signal and record all the data:

  • How long did it take from Rosetta to Philae? (Philae encoded this in the signal)
  • How long did it take from Philae back to Rosetta? (Rosetta compares the time of receiving the transponder signal with the encoded timestamp)
  • How faint was the signal, when Philae received it? (means: How large is the attenuation of the comet)
  • Did the polarization change?
  • Was the signal somehow otherwise modified? (e.g. phase-shift)

Rosetta and Philae will conduct multiple, many many thousand send-receive experiments and at the same time record their position. From all the data then ESA will be able to calculate the inner structure of the comet:

  • How many layers are there and how thick are these?
  • From which material is the comet made of?
  • What’s the density?
  • Are there regions in the comet more or less dense?
  • If yes, how do these look like?
Seismic Tomography

Seismic Tomography; this is an example of using earthquakes to determine the inner structure of earth; CONSERT will apply the same principle, the earthquakes are here the Radar-sender, the receiver an antenna instead of an seismometer. The Department of Earth & Atmospheric Sciences , Cornell University; Source: http://www.geo.cornell.edu/geology/classes/Geo101/101images_spring.html

CONSERT won’t be useful before Philae landed, but it’s a rather interesting instrument. Until now we can only guess about the internal composition of a comet. We made educated guesses, but you never now until you had a real look at it.


Rosetta: Expecting first light from OSIRIS

March 24, 2014

Just to remind everyone, for today it’s scheduled to let OSIRIS have a first look at 67P:

24 March – Pending successful re-activation, OSIRIS will take a first look in the direction of the comet. The comet will be too far away (around 5 million kilometres) to resolve in these first images and its light will be seen in just a couple of pixels. These images will be acquired regularly for navigation purposes and to already start planning the trajectory corrections planned for  May.

ROSETTA READY FOR PAYLOAD CHECK-OUT; 2014-03-05; ESA; Source: http://blogs.esa.int/rosetta/2014/03/05/rosetta-ready-for-payload-check-out/

OSIRIS is a camera with wide- and narrow-angle optics along with quite a few filters for different spectra and was covered in part 2 of the “All eyes on Rosetta” series.

In the meantime, here an older picture OSIRIS took before going to sleep:

. Colour composite of the Orion nebula M42, obtained with the OSIRIS NAC during commissioning

Colour composite of the Orion nebula M42, obtained with the OSIRIS NAC during commissioning; Keller et al. 2007, “OSIRIS – The Scientific Camera System Onboard Rosetta”; Figure 39; Page 39

I can’t wait for OSIRIS’ first light after ending hibernation.


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