Tag Archives: LRO

Chandrayaan-1: the Lost and Found Lunar Orbiter

This is pretty cool. ¬†ūüėČ

On October 22, 2008, India joined the elite group of nations which have successfully sent spacecraft to orbit the Moon. ¬†The mission was successful, conducting joint operations with NASA’s Lunar Reconnaissance Orbiter and LCROSS impactor, deploying an impactor of its own to help search for lunar ice (and making India only the fourth country to place its flag upon the Moon), and providing the first definitive proof of water ice in the lunar soil. ¬†The mission was cut short, however, when the spacecraft abruptly stopped responding to ground commands on August 29, 2009. ¬†The cause of the failure was never determined, but it had been experiencing issues in several systems, including the star tracker that keeps its antenna aligned with Earth.

Like other deep space spacecraft, the moment it stopped transmitting it became impossible to track from Earth — the Moon is much too far away to track such small objects (in Chandrayaan-1’s case, about 1.5 meters by 1.5 meters) by radar.

Or is it?

As international governmental and private space programs grow at an astonishing rate, it has become clear that space traffic will increasingly become a problem not just in Low Earth Orbit (LEO) and in the immensely valuable Geostationary Earth Orbit (GEO, the province of most communications satellites) but in deep space as well. ¬†The recent move of the MAVEN spacecraft to dodge Mars’ innermost moon, Phobos, also underscores the hazards. ¬†So JPL conducted a study to see whether lunar spacecraft actually¬†could be tracked from Earth. And guess what — they can!

JPL’s first target was LRO, because it’s an active spacecraft and therefore its real position is known with exquisite precision. ¬†Having located it with ground-based radar, the team moved on to something trickier: the Chandrayaan-1 spacecraft. ¬†Lunar spacecraft are difficult, because the Moon is so lumpy that a) dead spacecraft don’t stay long unless their orbits are fairly high, and b) orbits can be difficult to predict over long timescales. ¬†Nevertheless, they found it. ¬†Chandrayaan-1 is dead, but not gone, and certainly not forgotten.

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What’s a Supermoon?

There’s a lot of fuss¬†on the Internet right now about the supermoon, so you might be wondering: what is it? ¬†And what’s the big deal?

The easy answer: a “supermoon” is the biggest full moon of the year.

The long answer: the Moon doesn’t always cover exactly the same amount of sky — it can appear slightly larger or smaller depending on where it is in its orbit (although truthfully, the difference isn’t really perceptible). ¬†This is because the Moon isn’t always the same distance from us. ¬†Like most orbits, its orbit is elliptical, not circular, and the Earth (or, more accurately, the common center of mass) sits at one focus of the ellipse. ¬†The closest point is called periapsis (or perigee, when talking specifically about objects orbiting Earth), and the farthest point is called apoapsis (or apogee). The supermoon is, therefore, the full moon that occurs closest to perigee.

A full lunar cycle, or lunation (which is not exactly the same as a lunar orbit, but close), takes about 29 and a half days. ¬†This is also precisely the length of a lunar day, but about two days longer than the lunar orbit. ¬†This is because the Earth-Moon system is moving around the Sun, which affects the angle of sunlight. ¬†(This is also why there’s a difference between a solar day and a sidereal day. ¬†The former is how long it takes to go from midnight to midnight, and is what we set our clocks by, but the latter is how long it takes the Earth to complete one rotation with respect to the “fixed” stars.) ¬†So all this basically means the Moon will be at different points in its orbit when it hits different points in its cycle, but it may take a long time for the cycle to repeat. ¬†Tomorrow, the Moon will be the closest to perigee when it hits full moon than it has been since 1948. ¬†So that’s why people are calling it “the closest supermoon” or the “biggest supermoon”.

Now, what it¬†isn’t is the closest pass the Moon has made sine 1948. ¬†In fact, the last time the Moon was thi close was . . .

. . . a whopping 27 days ago. ¬†And it will be this close in another 27 days. ¬†It just won’t be full at the time.

Still, it’s kind of a cool thing. ¬†And the Lunar Reconnaissance Orbiter¬†team has put together this amazing visualization of all the lunations for 2016 — including the current one. ¬†They didn’t do it just for the supermoon; in fact they did this last year too. ¬†It’s a beautiful visualization of the process, showing just how much bigger or smaller the moon may appear, and showing at top left where the Moon is in its orbit (not to scale, but clearly indicating perigee and apogee). ¬†Skip to 4:24 to see the supermoon. ¬†Also notice how the Moon moves more quickly near perigee than apogee; the slider to the right, showing the Moon’s distance from Earth (to scale) is a good place to watch for this. ¬†They rendered this for both northern and southern hemisphere viewers; I’ve inserted both below:

 

By the way, this may also give you some insight into why not all solar eclipses can be total.  If there can be a perigee full moon, there can be perigee new moon as well, and all eclipses are at new moon.  A perigee solar eclipse will produce a total eclipse.  An apogee solar eclipse will produce only an annular eclipse; the Moon at perigee appears too small to cover the Sun completely.

 

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Making an Impact: Apollo 16 S-IVB Found!

Yesterday, I wrote about LRO’s astonishing new Earthrise image, and today I’ve got something else for you from LRO. ¬†This is a little old, but better late than never. ¬†ūüėČ ¬†Early this month, the LRO team announced that they’d found another piece of history — the impact site of the Apollo 16 S-IVB.apollo-16-s-ivb-impact-site-seen-by-lro

All the other S-IVBs that had impacted were easier to find because telemetry from the boosters had been maintained pretty much right up to impact.  But this one had gone silent before impact, so its precise trajectory was unknown.  But with a bit of patience, the team was able to find it.  Craters like this are invaluable, because their precise age is known, as well as the size and nature of the impactor.  Studying the weathering of the crater helps to improve crater dating methods.  This one is still very young, of course, but now that it has been found, it too can be monitored.

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Most Amazing Earthrise Ever, from LRO

Lunar Reconnaissance Orbiter almost never captures the Earth. ¬†After all, NASA has spent a lot of money to put it around the Moon to take pictures of that, and plus, it’s built as a mapping satellite. ¬†It’s designed to excel at scanning the terrain below it. ¬†Taking a picture of an object in the distance is not its strong suit. ¬†But with some planning, it can be done. ¬†And holy wow, is it worth the effort. ¬†Combining image data from the Narrow¬†Angle Camera and color data from the Wide¬†Angle Camera, this spectacular composite image shows the Earth rising over Compton Crater, a farside crater near the lunar limb. ¬†What’s really cool is seeing the silhouette of mountains still in shadow against the colorful disk of the Earth.

Feast your eyes, for this is us, from the Moon, on October 12 of 2015. ¬†(It’s taken this long to assemble the best possible quality image from all the data LRO returned.) ¬†It doesn’t look real. ¬†It looks CGI. ¬†But in fact it is completely real.

earth_and_limb_m1199291564l_color_2stretch_mask_0

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Tranquility Base in a new LRO video

The video is comprised of previously acquired imagery from Lunar Reconnaissance Orbiter, including the best ever imagery of the landing site, taken in 2012. ¬†It brings it to life, though, by rendering it in a three-dimensional flyover of the site and also showing how the images of the LM map to the original thing and the photographs taken at the site forty-five years ago. ¬†It’s quite lovely; check it out. ¬†ūüėČ

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And as Dragon goes up, LADEE goes down….

Actually, it went down late last night. ¬†But RIP LADEE, NASA’s latest lunar mission. ¬†LADEE’s mission was always¬†meant to end this way, a consequence of the low orbit it required to conduct its mission passing through the moon’s lumpy gravitational field and extremely tenuous atmosphere, and gradually easing lower to get ever more sensitive measurements. ¬†NASA does not yet know exactly where it came down, but have a general idea, and expect they’ll find the impact site by¬†searching through LRO imagery over the next few weeks. ¬†LADEE survived the eclipse last Tuesday, but ultimately succumbed to the inexorable pull of gravity. ¬†It was actually predicted to impact Sunday or MOnday, so it actually came down a little ahead of schedule. ¬†But the Moon’s mascons make lunar navigation difficult, especially as you get close, so a precise date was never possible.

Now comes the next part of the mission: analyzing the data it returned!

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So what does an eclipse look like from the Moon?

In the wee hours of Tuesday morning, we’ll be treated to a total lunar eclipse. ¬†But the spacecraft at the Moon will get a solar eclipse instead, as the Earth crosses in front of the Moon. ¬†The ringside observers at present consist of Lunar Reconnaissance Orbiter (which has already observed others, but spent its efforts looking at the Moon instead of the Earth, to see how the sunlight was changed by its passage through the Earth’s atmosphere), the Change’e 3 lander and rover Yutu*, and NASA’s LADEE spacecraft. ¬†This last is the one that scientists and engineers are most nervous about. ¬†LADEE is already near the end of its mission, due to declining hydrazine and nitrogen tetroxide reserves to maintain its orbit through the Moon’s lumpy gravity field. ¬†But unlike Change’e 3, which is built to survive two weeks of total darkness, LADEE is only built to survive very brief trips through the Moon’s shadow. ¬†Tuesday morning, it will be spending four hours transiting the various portions of the Earth’s shadow — penumbra, umbra, and then the other side of the penumbra. ¬†Its batteries will probably endure this, though it’s outside design parameters, but the hydrazine fuel has a fairly good chance of freezing. ¬†If it does, the mission will be effectively over as it will have no means of orienting itself. ¬†And if so, it is not a big loss, for the spacecraft has already completed its mission. ¬†Any science it uncovers during the eclipse is pure gravy, though gravy the team is anxiously awaiting all the same, like proud parents watching their child’s team strive to defeat the star team, ready to proud of whatever they achieve, but hoping against hope they do better than anyone had expected.

The various spacecraft at the Moon will attempt to observe the eclipse, or to observe the Moon during the eclipse. ¬†What will it look like? ¬†Well, here’s what the Japanese Kaguya probe saw during a penumbral eclipse (a relatively gentle occurance compared to a total lunar eclipse, as it’s over more quickly) in 2009, watching as the Earth rose over the lunar horizon due to the spacecraft’s orbital motion:

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*Yutu has survived the long lunar night after all, but is now stationary.  I have no information on how much science it is currently able to perform.

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