Friday, October 9, 2009

Space: LCROSS crashes into the Moon

Shortly, the US spacecraft LCROSS (Lunar Crater Observation and Sensing Satellite) will purposely crash into the Cabeus crater on the Moon's southern pole in the hunt for water-ice.

LCROSS and centaur on collision course


The spacecraft will impact in two stages, having separated last night. A large fuel stage called Centaur will impact first. With a mass of >2000KG striking the crater at over 9000kph (5600mph), the plume from the impact will be observed both by the main LCROSS spacecraft from close up, and a wide range of Earth based telescopes including Hubble. Observation should then be able to yield the chemical contents of the plume via spectroscopy.


The LCROSS "shepherding" stage will then follow on through this plume [NASA's projection - right] sending telemetry back to Earth, before impacting itself into the crater causing a second collision and plume of material.

Craters at the Moon's poles can remain in permanent shadow and hundreds of tons of water-ice are suspected to be exist. Confirmation of water-ice on the Moon would pave the way for the progress of humankind beyond our blue sphere, easing creation of a moon-base by many magnitudes.

Updates to follow after the event! You can watch the proceedings live on NASA TV.


Update 1 - The collisions


Nasa TV pictures showing flight plan and a shot of the Moon from LCROSS's close perspective.




3500 miles from the surface



Team seem to be having network troubles due to all the traffic flying about to other facilities, so are cutting webcam feeds to other parts of NASA.




Infra red and another even closer image:


 


About 13 minutes to impact


Changing the rates of the infra red feeds to compensate for dropped images. 10 minutes to impact!





Not long to go. They had to turn down the resolution of some instruments due to worries about exceeding the 1Mbps feed rate from the spacecraft. 5 mins out.





4 mins out.



2 mins out.



60 seconds.



In the following pictures centaur should have impacted. And we ride LCROSS into the surface..





 


We did not see a giant plume of dust from the first impact of centaur. It will probably take a few hours for NASA and all the observatories around the world and in space to process the data. NASA scientists are stating this is a good thing, as hitting muddy material is more desirable than dusty/rocky material.

The second impact of the LCROSS shepherd ship itself (which we rode in on in the above images) landed in a different crater, so even if centaur's impact failed to produce the desired effect, there is another chance with the data from the LCROSS collision.

LCROSS has been a low-cost and rapidly prototyped mission, in a new wave of space experiments. The "old" NASA would somewhat over design things, which we imagine will still be the process if astronauts are involved! But with low-cost missions such as LCROSS, science can be done quickly, and 3 or 4 spaceships like this one can be launched for the price of a single more expensive and engineered to perfection mission.


Update 2 - Post impact

The NASA post-impact press conference is underway now.

Dan Andrews (Project Manager) thanks the team, not just those that could be present at the conference.

Anthony Colaprete [left] (Principal Investigator) talks at length about what they've seen so far. There was an impact, and they've seen the crater of that impact event. They've got spectroscopy data which was the most critical thing, so now have everything they need to address the question of what the hydrogen detected in this area is.

He has been awake for 36 hours working on the mission, and has only had 15 minutes to look at the data so far. So what will be announced today isn't a definitive "yes" or "no" about water on the Moon.

He presents a series of slides:











The images show the impact crater of centaur, so we have a confirmed impact. However they do not show a readily visible plume. Of course these are very early days, and they have a ton of data to analyse. There's a blip on the first UV/Visible Radiance graph just before impact which he's excited about (before the larger blip at the end, believed so far to be a data anomaly at the death of the feed).

Considerable heat is detected at the crater, and he mentions sodium was detected in the initial spectroscopy results.

Jennifer Heldmann [left] (Observation Campaign Lead) talks at length about the processes gone through to coordinate so many telescopes on the Moon for this event.

Shows a series of images pre impact, taken from telescopes around the world:








Shows a series of telescope images during the event:










Including a "squiggly lines" image that scientists enjoy.

Then some videos were shown. The first showing an animation of centaur flying through space against the background of streaking stars.




 



They've got data from telescopes around the world, including in Hawaii, New Mexico and California. And space based observations from Hubble (data inbound during conference), the Luna Reconnaissance Orbiter, Odin, IKONOS, and GeoEye-1.

Mike Wargo (Chief Lunar Scientist) then talks about the mission, praising the science that will come of this moment. How this is what NASA should be doing, combining exploration and science in exciting missions like this. NASA makes dreams come true.


News media questions and answers (paraphrased)

Q: If you can see sodium, can't you check for water in the same data?
Anthony: Yes, we can. I've not looked yet though.
Q: Can't you call someone now and get them to say yes or no?
Anthony: I could, but we need to be careful before making claims one way or the other. We need to look at the data and make a case either for or against water.

Q: Will hubble images show the plume better?
Jennifer: HST is focused on spectroscopy, where the science is.
Q: Is there doubt about there being a plume at all?
Anthony: It's not in our initial image data, but we need to look further.
Mike: Remnants of the event are still ongoing,  the disturbance of the exosphere.
Anthony: Plus there are two impacts for all the observing telescopes, we only had centaur's to see from LCROSS.

Q: Any evidence the shepherd ship flew through a vapour cloud?
Tony: Can't say yet. But we had a high signal to noise ratio in our data. The impact crater showed up as 1 pixel, which implies its size in the 18-20m range.

Q: Any concerns about centaur spinning upon impact?
Anthony: The flicker of the spacecraft in the telescope captured flight videos might provide data about any spin rate.

Q: Gain on camera set correctly to view the plume?
Anthony: That's not been ruled out. The craft camera uses auto-gain. Manually managed the data rate on near-IR, as closer more detailed images take up more bandwidth of their 1Mbps connection. Only 40 images were dropped from the feed, which is very good. Cams have large dynamic range.
Q: Was the second impact supposed to be visible from Earth too?
Anthony: Just about. It should throw up some more stuff.

Q: If there's no water, are you looking for anything else?
Anthony: Science is science. Putting pieces of the puzzle together. Will see what happens first.
Q: Looking for anything except water?
Anthony: Everything. What's the source of the hydrogen? Sodium flash is interesting. The Moon swing by data from the craft will be released soon, and data from this mission in a couple months.

Q: How long to build the case for or against water? What do the spectra blips mean?
Anthony: This is the 2 hour mark. In 2 days we meet and choose who analyses what data. At 2 weeks we meet and discuss. In 2 months we present the findings to the world.

Q: How can you have a crater but no ejection?
Anthony: Great question. The process of impact is complex: matter didn't fly high enough? Hit rocks/slope on impact? Luck is needed, type of material and composition important. Shadow heights deeper than thought? etc.
Mike: We're crashing into something that hasn't seen light in about 2 billion years. This is exploration, doing experiments then moving on from there.

Q: Can this mission be a model for future missions, eg similar process for smacking into an asteroid.
Dan: It's being considered. The mission is novel, and space missions unforgiving. With lower complexity crafts like this the risks are lower, so it can definitely be applied elsewhere.

Q: (More about lack of plume) Surprised by lack of plume data? "Public disappointed".
Anthony: Not surprised, I expected to BE surprised. There's lots of built in redundancy in the experiment for if there isn't a massive plume, and I've only had 15 minutes to quickly scan the images from the Shepherd craft so far. There's a flash spectra, and it's looking promising for curtain spectra.
Mike: This is just the beginning. All the data analysis starts now.

Q: Why did sodium pop out as being interesting?
Anthony: We don't understand the lunar exosphere (equivilent of atmosphere). Means something has thermalised down in the crater, reactions have occured with the heat, sodium was excited. Why it got excited is a good question.

[Conference ends]


So there we have it. It wasn't as spectacular as some anticipated. But the capture of spectroscopy data should answer all the questions the mission set out to answer. And maybe provide us with some more questions!



Further reading
NASA: LCROSS homepage
BBC: US spacecraft set for Moon crash, US spacecraft crash into the Moon

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