Category: Moon

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The LCROSS spacecraft will be giving it all up for science Friday morning when it and the second stage of the Centaur rocket impact Cabeus crater on the Moon’s south pole, searching for possible water ice hidden inside the perpetually dark portions of the crater. Since we’ll never see LCROSS again, its only fitting to take a good long, last look at her. Solar System Ambassador and Planetary Society volunteer Ken Kremer had the wonderful opportunity to see both LCROSS and her sister ship the Lunar Reconnaissance Orbiter (LRO) in the Astrotech Space Operations Facility clean room in Titusville, FL earlier this year before the dynamic duo launched together on June 18. Ken has graciously given permission to allow us to publish these images (which were previously posted on the Planetary Society website) so we can all remember what she looked like. Above is a side view of LCROSS wrapped in gold multi-layer thermal insulation. The solar array is on the left side. Science instrument, avionics, navigation, communication and thruster equipment panels encircle and are attached to the central payload adapter ring. The star tracker is on the right side, and the payload fairing halves sit at either side.

More images below.

Here’s a picture of Ken with the two spacecraft. Visible are the solar arrays for LRO (top, left) and LCROSS (bottom, left). Visible is the LCROSS panel with the 9 science instruments (gold color) which run on just 100 watts of power. Above Ken’s head is the visible light camera.

This image really provides a reference to how big these two spacecraft actually are. Note the person in the bunny (clean) suit standing next to LRO (gray) and LCROSS (yellow) lunar spacecraft stacked adjacent to Atlas V payload fairing.

And since we’ve now seen LCROSS up close, here’s a few new close-up images just released by NASA of Cabeus crater.

This visualization image gives a bird’s-eye view of Cabeus crater and the target zone for the crash site. A 3.5-kilometer-wide “flagpole” marks the targeted location within the crater. Colored stripes on the pole indicate one kilometer steps in elevation above the crater floor, black stripes indicate 5 kilometer steps. The pole stands 25 kilometers tall, and the blue rings mark heights of 50 and 100 kilometers above the impact site.

This image shows key lunar landmarks used to locate Cabeus crater. The yellow scale shows angular distances in the plane of the impact site; blue arcs show heights 50, 100 and 200 kilometers above it.

And click here for a link to a video visualization that zooms into Zoom into the Moon as it might look shortly after the LCROSS impact. Blue arcs represent 50, 100 and 200 kilometer heights above the crash site.

Hopefully the telescopes trained on this region of the Moon will give us the real images of this event!

Lead image caption: LCROSS Close Up. Side view of LCROSS wrapped in gold colored multi layer thermal insulation. Note solar array at left. Science instrument, avionics, navigation, communication and thruster equipment panels encircle and are attached to the central payload adapter ring. Star tracker at right. Payload fairing halves sit at either side.
Credit: Ken Kremer

Sources: Ken Kremer and the Planetary Society Blog, Goddard Space Flight Center

There seems to be a little lunacy making the rounds that NASA is going to “bomb” the Moon on Friday morning, or “hurt the Moon,” or “split the Moon in half,” or change its orbit. This is all just nonsense and scare-mongering, and those worried about our Moon can rest assured our lunar companion will remain in the sky relatively unchanged after this experiment to search for water ice on the Moon’s south pole. Let’s take a look at the physics involved and what might happen to the Moon.

First of all, there are no explosives involved. The LCROSS mission is going sending a upper stage of a Centaur rocket and a smaller spacecraft to impact the Moon. The two objects will create a crater — The 5,000-pound (2,270-kilogram) Centaur is expected to slam into Cabeus Crater on the Moon’s south pole at a sharp angle at a speed of 5,600 mph (9,000 kilometers per hour). The Centaur’s collision is expected to create a crater roughly 60 or 70 feet wide (20 meters wide) and perhaps as much as 16 feet (5 meters) deep, ejecting approximately 385 tons of lunar dust and soil — and hopefully some ice.

The LCROSS spacecraft itself, weighing in at 1,500-pounds (700-kilograms), will follow the Centaur by about four minutes and fly through the regolith plume thrown up by the collision, just before it too slams into the lunar surface, kicking up its own smaller plume of debris, all the while using its sensors to look for telltale signs of water, beaming the information back to Earth.

So, yes, it will make a rather big crater on the Moon. But one close-up look at the lunar surface will reveal that the Moon is full of craters, and still regularly receives hits by meteorites and larger space rocks – not as much as in the past, as most of the craters on the Moon are from an earlier period in our history when there was more debris left over from the formation of the solar system. The Moon was not “hurt” in the past, and it will not get hurt by this impact. Additionally, other spacecraft have hit the lunar surface with no adverse effects on the Moon or its orbit.

But will this impact change the Moon’s orbit? Dr. Jeff Goldstein from the National Center for Earth and Space Science Education writes about this on his blog, Blog on the Universe:

The Atlas V Centaur upper stage has a mass of 2,000 kg (the more massive of the two vehicles impacting the Moon). It will be moving at 5,600 mph (2.5 km/sec.) BAM! By comparison, the Moon is orbiting the Earth at the measely speed of 2,300 mph (1.022 km/sec). On the other hand, the Moon is just a tad bit more massive than the specks on a collision course.

So let’s say we wanted to change the Moon’s speed by JUST 1 MPH (0.0004 km/sec)—which is less than 1/2,000th its orbital speed—and we were going to do it by hurling Atlas V Centaur upper stages at the Moon. How many would we have to hurl its way? HEY, let’s give every person on planet Earth an opportunity to hurl one. Would that do it? Uh … nope. Every person on Earth (all nearly 7 billion of us) would each need to hurl 1 MILLION Atlas V Centaur upper stages at the Moon. I’d rather just hurl one and not worry about it. Rest easy, sleep well, and let’s see if we can find water on the Moon at the South Pole.

Another question people have been asking: Will the impact destroy the water we are looking for?

NASA answers that question on the LCROSS FAQ site:

The LCROSS impact will have the same effect on the water (if it is indeed there) as any other object that might naturally impact it. Most (>90%) of any water that is excavated by LCROSS will most likely return to nearby “cold traps”. The LCROSS impact is actually a slow impact and, thus, most of the material is not thrown very high upward, rather outward, adjacent to the impact site. Of the water that does get thrown upward, much of it will actually return to the Moon and eventually find its way back to the dark, cold craters. This is actually one possible way that the water was supplied in the first place: it was deposited following the impacts of comets and asteroids.

There is about 12,500 square km of permanently shadowed terrain on the Moon. If the top 1 meter of this area were to hold 1% (by mass) water, that would be equivalent to about 4.1 x 1011 liters of water! This is approximately 2% the volume of the Great Salt Lake in Utah. The LCROSS impact will excavate a crater approximately 20 meters in diameter, or about one-trillionth the total permanently shadowed area. It is safe to say the LCROSS impact will not have a lasting effect on lunar water, if it does indeed exist.

See our previous article on how to watch the LCROSS event.

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The LCROSS spacecraft is going to impact the Moon on Friday, October 9, and here’s your chance to watch the action, either just for fun, or to contribute to scientific observations. Whether you want to observe with your own equipment or watch the event on television or a webcast, below you’ll find all the information and links you should need to be a part of history. Amateur astronomers need a 10-inch or bigger telescope to make observations.

When: Following the latest trajectory correction maneuvers, the time of impact on Friday, October 9, 2009 is 11:31:19 UTC for the Centaur and 11:35:45 for LCROSS spacecraft (7:31:19 a.m. EDT and 7:35:45 a.m. EDT).

The impact time may be refined as the time for impact comes closer. You can check the LCROSS mission Facebook and Twitter pages for the latest updates (and we’ll try to post it here as soon as possible after any changes are announced.) Also check this NASA website for more information.

Where: both spacecraft are targeting Cabeus crater. The impact site coordinates are -84.675, 311.275 E. Click here to download the Targeting Coordinates, Timing, and Finder Charts presentation for detailed information. (Powerpoint presentation.)

New Mexico State University and Marshal Space Flight Center have made finder charts available based on similar illumination and libration that we expect to see on the night of the impact.

In general, here’s where to look: Start with the south pole (bottom edge) and look for the terminator, or where the sunlight and shadow merge. Here’s what the Moon should look like:

Zoom in with your telescope and identify the Cabeus craters. The target is in Cabeus proper, near the bottom of the Moon. Here’s what it should look like, along with a notated image:

What will I see? Based on an projections, there should be a visible ejecta cloud rising to 6Km above the lunar surface and crater wall. Latest estimates of the Cabeus proper crater impact site indicate the first two or three kilometers of that plume height (the brightest parts) may not be viewable from Earth, but that the plume will hopefully have crater wall shadow behind it to help us see it. Impact design location is to maximize the amount of this in sunlight, but variables here will determine how much of it is actually illuminated, and it may be that only the high power instruments will see good contrast. But we don’t know for sure.

“We expect the debris plumes to be visible through mid-sized backyard telescopes—10 inches and larger,” says Brian Day of NASA/Ames. Day is an amateur astronomer and the Education and Public Outreach Lead for LCROSS. “The initial explosions will probably be hidden behind crater walls, but the plumes will rise high enough above the crater’s rim to be seen from Earth.”

See this page for more information.

What is actually going on? The 5,000-pound (2,270-kilogram) Centaur is expected to slam into Cabeus at a sharp angle at a speed of 5,600 mph (9,000 kilometers per hour). If all goes according to schedule, the shepherding vehicle, carrying nine science payloads, will follow the Centaur’s plunge into the moon, and send back data live to Earth. The Centaur’s collision is expected to create a crater roughly 60 or 70 feet wide (20 meters wide) and perhaps as much as 16 feet (5 meters) deep, ejecting approximately 385 tons of lunar dust and soil — and hopefully some ice. In addition to recording the collision, the shepherding spacecraft weighing, 1,500-pounds (700-kilograms) will fly through the regolith plume thrown up by the collision, just before it too slams into the lunar surface some four minutes later, kicking up its own smaller plume of debris, all the while using its sensors to look for telltale signs of water.

What if it is cloudy where I live, or I live in Europe/Asia and it is daytime, or I don’t have a telescope to watch?

You can watch the event on NASA TV, and here’s where you can watch it online.

Slooh is having a webcast and will have two telescopes trained on the impact site.

The Exploratorium is also showing a webcast.

If you want to watch with other space enthusiasts, check out this list of people and organizations that are sponsoring observing parties.

Also, if you are in Mumbai, India the Nehru Planetarium there has a free viewing of the event at 4 pm IST. (thanks for pradx on Twitter for that info.)

If you are in the Pasadena area, JPL’s Von Karman Auditorium will have a public viewing, opening the gates 3:00 am. local time.