While we're waiting for Those Pictures, here are a couple of shots of LCROSS from our campus observatory last night (0221, 027 UT on 15 July). 4 minute exposures tracking expected motion from the Horizons ephemeris, within 20 degrees of the southern horizon and fighting summertime haze as well as city lights. I wanted to catch it before its inclined orbit takes it too far south, after which it spends a week or so as a predawn object. The range was about 563,000 km, and the Centaur is no bigger than a CSM/LM combination, so this is a more difficult target than spotting an Apollo enroute was. (On the other hand, nobody had CCD imagers in 1969).
Click to view attachment
Full Version: LCROSS en route
Sweet!!!
What's your campus scope, anyhow? (Type, aperature, etc.)
What's your campus scope, anyhow? (Type, aperature, etc.)
0.4m Ritchey-Chretien, using one of the big Santa Barbara Instruments CCDs for this. Details here. I have been very pleased with its performance (installed about 5 years ago, replacing a vintage-1950 refractor). With our summer climate, I am also very pleased that it can be operated from an air-conditioned control room! Perspiration is bad for the logbook, not to mention keyboard.
An article on the "cold side bake-out" process (to get rid of water contained in the Centaur stage's foam layer) can be found here: http://www.spaceflightnow.com/lcross/090810bakeout/
Two bakeouts have been completed, with at least one more to go.
The target crater for the impat will be decided upon early September, and NASA tentatively plans to announce the target crater around Sept. 10.
Last week, LCROSS looked back at Earth as part of an calibration of its science payload. More details can be found here: http://www.nasa.gov/mission_pages/LCROSS/main/
Two bakeouts have been completed, with at least one more to go.
The target crater for the impat will be decided upon early September, and NASA tentatively plans to announce the target crater around Sept. 10.
Last week, LCROSS looked back at Earth as part of an calibration of its science payload. More details can be found here: http://www.nasa.gov/mission_pages/LCROSS/main/
LCROSS experienced an anomaly: http://www.nasa.gov/mission_pages/LCROSS/main/index.html
Oh, this is BAD! But they are optimistic that the mission will be fulfilled despite the problem.
Wow. Is the IRU in question part of the Centaur itself? That would sort of make sense of such a dramatic fault, since booster components ordinarily aren't expected to operate longer than a few hours at the most.
Hmm, I thought star trackers were the de facto method of maintaining/figuring out attitude with gyros only as backups for periods when star trackers are unavailable? 
There were some initial problems with the star tracker (STA) and the IRU (June 26) after launch, however, these were minor, expected, problems -- according to the Flight Director's Blog.
As far as I understand, the ACS Attitude Control System is "based primarily on LRO hardware and software in the same arrangement". Tried finding some images of the IRU, the ACS, however, no luck -- assuming that they are on the LCROSS R4 (Attitude Control & Communications Electornics) panel.
John
A Moon Site
As far as I understand, the ACS Attitude Control System is "based primarily on LRO hardware and software in the same arrangement". Tried finding some images of the IRU, the ACS, however, no luck -- assuming that they are on the LCROSS R4 (Attitude Control & Communications Electornics) panel.
John
A Moon Site
On August 17, LCROSS took additional images of the moon and earth, as part of the process to calibrate its instruments. See page http://www.nasa.gov/mission_pages/LCROSS/main/index.html
Here's a Spaceflight article explaining the recent startracking-frenzy anomaly:
http://spaceflightnow.com/lcross/090825fuel/
summary: Half the fuel is gone, but it should be just enough to complete the mission. LCROSS may have to cancel some activities not crucial to the mission to save the fuel for other unexpected contingencies.
In response to the Spaceflight Now article, this response from the LCROSS team...
During a communications session on Aug. 22, it was discovered that a fault had been triggered in the spacecraft's inertial reference unit, or IRU. The IRU is used by the probe's attitude control system to determine its orientation in space.
The fault in the IRU caused LCROSS to switch to its star tracker for attitude information. Noise in the star tracker resulted in the spacecraft's attitude control system firing the spacecraft's thrusters excessively, consuming a substantial amount of propellant.
The mission operations team was able to correct the situation and stop the excessive thruster firing. Mission engineers determined what went wrong and uploaded software updates that should prevent such an incident from recurring.
The big issue was determining how much propellant was lost and how much was required to successfully complete the mission. The good news out of all of this is that the problem was caught and corrected in time so that the spacecraft still maintains a positive propellant margin; we still have more than enough propellant to successfully complete the mission. However, our extra margin of propellant is not nearly as much as it was previously. Mission management and the operations team want to maintain a prudent propellant margin for the rest of the mission and are therefore looking at the schedule of upcoming maneuvers to determine which are really necessary and which we can do without.
The bottom line here is:
1. An anomaly occurred which caused excessive use of propellant on the spacecraft.
2. The anomaly was detected and corrected.
3. Even after the anomaly, we have enough propellant to complete the mission.
4. We are still on target for a October 9 impact at 11:30 UT.
I know we promised you an exciting mission, but we are all looking forward to toning down the excitement until impact!
...End Message.
During a communications session on Aug. 22, it was discovered that a fault had been triggered in the spacecraft's inertial reference unit, or IRU. The IRU is used by the probe's attitude control system to determine its orientation in space.
The fault in the IRU caused LCROSS to switch to its star tracker for attitude information. Noise in the star tracker resulted in the spacecraft's attitude control system firing the spacecraft's thrusters excessively, consuming a substantial amount of propellant.
The mission operations team was able to correct the situation and stop the excessive thruster firing. Mission engineers determined what went wrong and uploaded software updates that should prevent such an incident from recurring.
The big issue was determining how much propellant was lost and how much was required to successfully complete the mission. The good news out of all of this is that the problem was caught and corrected in time so that the spacecraft still maintains a positive propellant margin; we still have more than enough propellant to successfully complete the mission. However, our extra margin of propellant is not nearly as much as it was previously. Mission management and the operations team want to maintain a prudent propellant margin for the rest of the mission and are therefore looking at the schedule of upcoming maneuvers to determine which are really necessary and which we can do without.
The bottom line here is:
1. An anomaly occurred which caused excessive use of propellant on the spacecraft.
2. The anomaly was detected and corrected.
3. Even after the anomaly, we have enough propellant to complete the mission.
4. We are still on target for a October 9 impact at 11:30 UT.
I know we promised you an exciting mission, but we are all looking forward to toning down the excitement until impact!
...End Message.
Good info, all (thanks for the late-breaking, Astro0!) Yes, by all means, let's save the rest of the excitement for The Day.
Didn't realize that LCROSS' ACS was designed to torque the entire stack around...amazing engineering, and undoubtedly some pretty unique control algorithms at work there.
Didn't realize that LCROSS' ACS was designed to torque the entire stack around...amazing engineering, and undoubtedly some pretty unique control algorithms at work there.
More good news: http://www.spaceref.com/news/viewsr.html?pid=32291
Nice memo to the LCROSS team and well deserved.
I am sure that they know how much effort the DSN put in also providing continuous coverage for LCROSS.
Also, how other missions made way in the schedule for them.
On UMSF we get to see the pretty pictures and data, but the effort that goes in to getting this stuff for us is incredible.
I've watched our comms teams during spacecraft emergencies and I can tell you it's incredible to watch so many people come together to solve sometimes seemingly unsolvable problems and all in real-time (and even two-way light travel time!).
I'm going to have to write a book one day about all the backroom happenings
I am sure that they know how much effort the DSN put in also providing continuous coverage for LCROSS.
Also, how other missions made way in the schedule for them.
On UMSF we get to see the pretty pictures and data, but the effort that goes in to getting this stuff for us is incredible.
I've watched our comms teams during spacecraft emergencies and I can tell you it's incredible to watch so many people come together to solve sometimes seemingly unsolvable problems and all in real-time (and even two-way light travel time!).
I'm going to have to write a book one day about all the backroom happenings
QUOTE (Astro0 @ Sep 6 2009, 01:37 AM) 
I'm going to have to write a book one day about all the backroom happenings
Oh yes, PLEASE do it. This is the kind of stories I'm badly looking forward to read.
I realise that we, in UMSF, are very pleased when a PI is given words in the forum, but YOU are also inside... and on all UM missions!!!
Thanks for your so valuable inputs.
QUOTE (Astro0 @ Sep 5 2009, 07:37 PM)
I'm going to have to write a book one day about all the backroom happenings
Cassini status reports do a good job of just saying it like it is. It often leaves me befuddled, but this is pretty clear:
QUOTE
Saturday, Aug. 29 (DOY 241):
Due to ongoing issues with the LCROSS spacecraft, it was requested that Cassini give up the beginning of two DSN tracks on DOY 241 and 243. For DOY 241, DSN schedulers were able to obtain a short DSS-55 track to maintain the full OTM-215 uplink window. On DOY-243, the decision was made - with the concurrence of project management - to accept the science data loss. This will result in approximately 45 MB of data that will not be seen on the ground due to the loss of DSS-65 track time.
Due to ongoing issues with the LCROSS spacecraft, it was requested that Cassini give up the beginning of two DSN tracks on DOY 241 and 243. For DOY 241, DSN schedulers were able to obtain a short DSS-55 track to maintain the full OTM-215 uplink window. On DOY-243, the decision was made - with the concurrence of project management - to accept the science data loss. This will result in approximately 45 MB of data that will not be seen on the ground due to the loss of DSS-65 track time.
...We can see at least one of the actions.
Just announced: impact in Cabeus A
Quick question regarding DSN time between Cassini and LCROSS. Can't Cassini just transmit the data at another time?
Anybody see any graphics online anywhere? I've looked at NASA, ARC, and LCROSS sites and come up empty.
FWIW, this post over at the NSF.com forum has an image of the "best pre-LRO, Lunar Prospector neutron data" showing the location of the selected site. Unfortunately, I cannot access the referenced paper, maybe others will have more luck.
Cabeus A crater location...the impacts should be visible for some of us...WOOT 
Click to view attachment
Image: (Left) Shaded relief map; (Middle and Right) Lunar Orbiter views; (Inset) Cabeus A crater region. North up, West left.
See NASA story
-----------------------
John
A Moon Site
Click to view attachment
Image: (Left) Shaded relief map; (Middle and Right) Lunar Orbiter views; (Inset) Cabeus A crater region. North up, West left.
See NASA story
-----------------------
John
A Moon Site
"Quick question regarding DSN time between Cassini and LCROSS. Can't Cassini just transmit the data at another time?"
No, it gets written over by new data. Only the highest priority data is protected from that.
Phil
No, it gets written over by new data. Only the highest priority data is protected from that.
Phil
The above link doesn't work for me; try this one:
LCROSS Reveals Target
There is a labeled telescopic image of the South Pole:
http://www.nasa.gov/images/content/385735m...SS_medium-1.jpg
A little thought please - do not put large images straight into a thread - Admin
LCROSS Reveals Target
There is a labeled telescopic image of the South Pole:
http://www.nasa.gov/images/content/385735m...SS_medium-1.jpg
A little thought please - do not put large images straight into a thread - Admin
For those who missed the briefing here it is on Youtube
http://www.youtube.com/watch?v=Y9RAWPBoi3I
I had planned to watch it but work got in the way.
Craig
http://www.youtube.com/watch?v=Y9RAWPBoi3I
I had planned to watch it but work got in the way.
Craig
Thank you for posting that very informative press conference,
my question would be - is the final target permanently shadowed ?
my question would be - is the final target permanently shadowed ?
For those hoping to see the impact; here're the Moon phases for October 2009:
http://www.moonconnection.com/moon-october-2009.phtml
A cadre of professional astronomers using many of the Earth's most capable observatories is helping maximize the scientific return from the LCROSS impacts. These observatories include the Infrared Telescope Facility and Keck telescope in Hawaii; the Magdalena Ridge and Apache Ridge Observatories in New Mexico and the MMT Observatory in Arizona; the newly refurbished Hubble Space Telescope; and the Lunar Reconnaissance Orbiter, among others.
I'm also looking forward to what images amateur astronomers will come up with. NASA plans a Citizens' science website for those...
http://www.moonconnection.com/moon-october-2009.phtml
A cadre of professional astronomers using many of the Earth's most capable observatories is helping maximize the scientific return from the LCROSS impacts. These observatories include the Infrared Telescope Facility and Keck telescope in Hawaii; the Magdalena Ridge and Apache Ridge Observatories in New Mexico and the MMT Observatory in Arizona; the newly refurbished Hubble Space Telescope; and the Lunar Reconnaissance Orbiter, among others.
I'm also looking forward to what images amateur astronomers will come up with. NASA plans a Citizens' science website for those...
Here a GIF animation of the Moon phase and the visibility/location of Cabeus A for "earthbound" watchers for October 09. Though, timing is bad 
http://greuti.ch/astro/LCROSSimpact.gif
I tried to match this image as good as possible.
Telescope views: http://groups.google.com/group/lcross_obse...b/finders?hl=en
And wow: http://www.pbase.com/slammel/image/104360794/original
http://greuti.ch/astro/LCROSSimpact.gif
I tried to match this image as good as possible.
Telescope views: http://groups.google.com/group/lcross_obse...b/finders?hl=en
And wow: http://www.pbase.com/slammel/image/104360794/original
Target crater switched from Cabeus A to Cabeus (proper)
http://www.nasa.gov/mission_pages/LCROSS/main/index.html
http://www.nasa.gov/mission_pages/LCROSS/main/index.html
I would think that they'll probably aim for the red-boxed region (right) as shown in the image below?
However, as to why Cabeus A was chosen initially is a puzzle as looking at the water equivalent hydrogen image (left), that while Cabeus A (Cabeus A1, really) has a much higher concentration (purple rectangle), its area is very much smaller to those of Cabeus and Cabeus B regions (oranges/reds) where the concentrations are smaller, but likely of successfully hitting them is better, isn't it?
John
------------
A Moon Site
Click to view attachment
However, as to why Cabeus A was chosen initially is a puzzle as looking at the water equivalent hydrogen image (left), that while Cabeus A (Cabeus A1, really) has a much higher concentration (purple rectangle), its area is very much smaller to those of Cabeus and Cabeus B regions (oranges/reds) where the concentrations are smaller, but likely of successfully hitting them is better, isn't it?
John
------------
A Moon Site
Click to view attachment
http://www.nasa.gov/pdf/386497main_target-selection_web2.pdf
This link goes to a c. 12 MB PDF on target selection. Page 8 has a map showing a more likely location. May not be exact, but pretty close. (see also p. 19)
Phil
This link goes to a c. 12 MB PDF on target selection. Page 8 has a map showing a more likely location. May not be exact, but pretty close. (see also p. 19)
Phil
Thanks Phil
Page 19 is very useful and probably more relevant, (the yellow dots in p8 are more than likely just ID crater centres).
As this is a Sept 5 publication and the text is still referring to Cabeus A to be the main target (p23 and elsewhere), the target corrections will undouptedly be refined down the closer to impact date.
Whatever one is chosen, however, it's sure to be a good'un
John
Page 19 is very useful and probably more relevant, (the yellow dots in p8 are more than likely just ID crater centres).
As this is a Sept 5 publication and the text is still referring to Cabeus A to be the main target (p23 and elsewhere), the target corrections will undouptedly be refined down the closer to impact date.
Whatever one is chosen, however, it's sure to be a good'un
John
Note that in the Colaprete report the Earth observability constraint is actually violated by the Cabeus site that is now the preferred target.
In return for a 50% gain in the Pixon signal (listed as criterion #2), they accepted a 125% increase (0.63 to 1.42) in the solar mask (criterion #1) and almost a ninefold
increase (0.33 to 3.07) in the earth observability mask (criterion #3). It's kind of hard to reconcile the ex-ante criteria with the subsequently revealed preference
unless the key lies in page 2 "Data not released to the public by individual Projects and Principal Investigators has been removed." To be accurate, that would have to cover the subsequently discovered data too, of course.
In return for a 50% gain in the Pixon signal (listed as criterion #2), they accepted a 125% increase (0.63 to 1.42) in the solar mask (criterion #1) and almost a ninefold
increase (0.33 to 3.07) in the earth observability mask (criterion #3). It's kind of hard to reconcile the ex-ante criteria with the subsequently revealed preference
unless the key lies in page 2 "Data not released to the public by individual Projects and Principal Investigators has been removed." To be accurate, that would have to cover the subsequently discovered data too, of course.
The latest release did refer to new topographic data showing better illumination than they had anticipated. The Earth observability mask would be very dependent on the exact location chosen, so a small move could alter it significantly.
I really want a map showing the exact location! Also, this is the Centaur target. The second impact site has not been announced yet. It would be nearby, but Colaprete talked about it at LPSC in March 09, responding to a question from me, saying that it might go to a spot with different illumination conditions, like the edge of a permanent shadow area if the Centaur went deep into the shadow area.
Phil
I really want a map showing the exact location! Also, this is the Centaur target. The second impact site has not been announced yet. It would be nearby, but Colaprete talked about it at LPSC in March 09, responding to a question from me, saying that it might go to a spot with different illumination conditions, like the edge of a permanent shadow area if the Centaur went deep into the shadow area.
Phil
Ask and ye shall receive I asked your questions of Tony Colaprete. He replied that he was hoping to get a map released today, and that the LCROSS ship itself would be targeted somewhat (3 km) away from the Centaur site in order to test a different location.
--Emily
I asked your questions of Tony Colaprete. He replied that he was hoping to get a map released today, and that the LCROSS ship itself would be targeted somewhat (3 km) away from the Centaur site in order to test a different location.--Emily
Here's a map of the approximate locations of the three polar impacts - LCROSS (counting as one) and MIP and Lunar Prospector. Only approximate as we still don't have actual coordinates for MIP or the LCROSS target.
I have taken the Cabeus area from LOLA data. It's much better shown here than on the current map on the LCROSS website, which appears to show Cabeus with half its real diameter. That older map is derived from an outdated USGS relief drawing.
Phil
Click to view attachment
I have taken the Cabeus area from LOLA data. It's much better shown here than on the current map on the LCROSS website, which appears to show Cabeus with half its real diameter. That older map is derived from an outdated USGS relief drawing.
Phil
Click to view attachment
What are the coordinates of the different impact sites?
--Emily
--Emily
The Google group of LCROSS (amateur) Observation has updated its page too: http://groups.google.com/group/lcross_obse...ion/web/finders
QUOTE
Cabeus has selenolographic coordinates of 84.9°S 35.5° W. The target PSR's coordinates have not been official announced but are estimated at approximately 84.4°S 45.0°W
From the Observation Group website:
-------------------------
Hello Team!
Latest update on impact locations:
Centaur: -84.70, 310.95E
SSC: -84.77, 310.45E
These are final and should not change.
Nominal timing for impacts:
Centaur = 9 Oct 2009 11:31:30 UTC
SSC = 9 Oct 2009 11:35:45 UTC
There may be some variation from these nominal times through remaining
trajectory correction maneuvering. We will post updates to these times
as they become available. Any timing updates on impact night will be
posted to LCROSS Twitter page, LCROSS Facebook page, and LCROSS-CS.
Brian
----------------------
Final LCROSS Centaur and SSC target coordinates (Lat., Lon. in ME)
Centaur: -84.675, 311.275 E
SSC: -84.729, 310.64 E
Elevations (Assumed Lunar radius: 1737.4 km):
Centaur target elev: -3.82693 km
SSC target elev: -3.80909 km
Impact Times:
Centaur: 9 Oct 2009 11:31:30 UTC
SSC: 9 Oct 2009 11:35:45 UTC
Note: These are nominal impact positions and times. Actual impact
times based on TCM results may differ (see next slide for
uncertainties)
----------------------------
That point is slightly west of the position shown on my map.
Phil
-------------------------
Hello Team!
Latest update on impact locations:
Centaur: -84.70, 310.95E
SSC: -84.77, 310.45E
These are final and should not change.
Nominal timing for impacts:
Centaur = 9 Oct 2009 11:31:30 UTC
SSC = 9 Oct 2009 11:35:45 UTC
There may be some variation from these nominal times through remaining
trajectory correction maneuvering. We will post updates to these times
as they become available. Any timing updates on impact night will be
posted to LCROSS Twitter page, LCROSS Facebook page, and LCROSS-CS.
Brian
----------------------
Final LCROSS Centaur and SSC target coordinates (Lat., Lon. in ME)
Centaur: -84.675, 311.275 E
SSC: -84.729, 310.64 E
Elevations (Assumed Lunar radius: 1737.4 km):
Centaur target elev: -3.82693 km
SSC target elev: -3.80909 km
Impact Times:
Centaur: 9 Oct 2009 11:31:30 UTC
SSC: 9 Oct 2009 11:35:45 UTC
Note: These are nominal impact positions and times. Actual impact
times based on TCM results may differ (see next slide for
uncertainties)
----------------------------
That point is slightly west of the position shown on my map.
Phil
Here's the latest info from Tony Colaprete, via the LCROSS Observation Group:
http://lcross.arc.nasa.gov/docs/LCROSS_Tar...date_100209.ppt
LCROSS Observation Group:
http://groups.google.com/group/lcross_observation
And a modified version of his map:
Click to view attachment
"Centaur Impact indicated by Red circle, SSC impact indicated by Blue circle"
The shading is LOLA elevation, not hydrogen abundance.
Phil
http://lcross.arc.nasa.gov/docs/LCROSS_Tar...date_100209.ppt
LCROSS Observation Group:
http://groups.google.com/group/lcross_observation
And a modified version of his map:
Click to view attachment
"Centaur Impact indicated by Red circle, SSC impact indicated by Blue circle"
The shading is LOLA elevation, not hydrogen abundance.
Phil
QUOTE (Phil Stooke @ Oct 3 2009, 06:06 AM)
Nominal timing for impacts:
Centaur = 9 Oct 2009 11:31:30 UTC
SSC = 9 Oct 2009 11:35:45 UTC
Centaur = 9 Oct 2009 11:31:30 UTC
SSC = 9 Oct 2009 11:35:45 UTC
Thanks Phil, this is very useful. Updated my realtime simulations with that info. Having troubles finding anything of a timeline of upcoming events, or the very latest trajectory info for that matter - the data on the Horizons system has LCROSS going through the moon
and I could not find any SPICE kernels. Unfortunately I'll be on the road for most of next week and can only "tweak" my existing trajectory data to match predicted impact times, can't process SPICE kernels on the road.
That's better!
The recent DIVINER image is proving quite useful to 'see' the area they're aiming at... LINK ...looks like it's in a shallow spot of two small merged impact craters.
John
The recent DIVINER image is proving quite useful to 'see' the area they're aiming at... LINK ...looks like it's in a shallow spot of two small merged impact craters.
John
This is what I get by overlaying Colaprete's map over Diviner to check the position.
Phil
Click to view attachment
Phil
Click to view attachment
Isn't that exact same as in my link above?
John
I don't know - but you inline quoted everything from the previous quote. Stop it. Final warning. Further posts will just be deleted - ADMIN
It's the image processing that's different.
Phil
Phil
Here's the map comparison that interests me: The target and water concentration maps:
The purple pixels in the old target area indicate (possibly) 1.7% water, the orange pixels of the the new target indicate 1%. As I understand it, the lower concentration of water in the new target area is offset by better viewing of the results. I wonder if there was also a little discomfort in relying on a signal of two purple pixels as opposed to a genuine patch of orange.
It seems to me that the new target is at the very edge of the orange patch. Perhaps that's the result of different viewing angles in the two images?
Click to view attachment
The purple pixels in the old target area indicate (possibly) 1.7% water, the orange pixels of the the new target indicate 1%. As I understand it, the lower concentration of water in the new target area is offset by better viewing of the results. I wonder if there was also a little discomfort in relying on a signal of two purple pixels as opposed to a genuine patch of orange.
It seems to me that the new target is at the very edge of the orange patch. Perhaps that's the result of different viewing angles in the two images?
Click to view attachment
Also the map of hydrogen concentrations is very model-dependent. The data were low resolution, and a model tries to show where it might be concentrated to give the blurry result actually observed. They will have better data now from LRO and other spacecraft, and that's probably what they preferred to use rather than the older model.
Phil
Phil
This is a comparison of the points John and I matched. They are very close but not exactly the same. I should point out that Tony Colaprete's circles don't reflect uncertainties. If they did they would not be the same size. The SSC uncertainty is about 3x greater due to the separation burn.
Phil
Click to view attachment
Phil
Click to view attachment
QUOTE (centsworth_II @ Oct 5 2009, 05:59 AM)
As I understand it, the lower concentration of water in the new target area is offset by better viewing of the results.
No, that's not true unfortunately. This document (http://www.nasa.gov/pdf/386497main_target-selection_web2.pdf) shows that the new target crater Caebus has *far* worse viewing conditions than Caebus A.
Caebus A Sun Mask Height: 630m, Caebus A Earth Mask Height: 330m
Caebus Sun Mask Height 1420m, Caebus Earth Mask Height 3070m
This is quite bad news -- they're sacrificing a lot of water sensitivity due to the sunlight/Earth masking. There must have been something seriously wrong with Caebus A to warrant this, as the mask heights at Caebus A are absolutely perfect for an experiment like this. I'm guessing that new LRO data must have either indicated a very uneven distribution or lack of water in the old target.
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