Viewing the South Pole of Vesta. This image obtained by Dawns framing camera and shows the south pole of the giant asteroid Vesta. Scientists are discussing whether the circular structure that covers most of this image originated by a collision with another asteroid, or by internal processes early in the asteroid's history. Images in higher resolution from Dawn's lowered orbit might help answer that question. The image was recorded from a distance of about 1,700 miles (2,700 kilometers). The image resolution is about 260 meters per pixel. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Take us into orbit Mr. Sulu!
The Dawn science team has released two spectacular rotation movies of the entire globe of the giant asteroid Vesta. The flyover videos give the distinct impression that you are standing on the bridge of the Starship Enterprise and gazing at the view screen as the ship enters orbit about a new planet for the first time and are about to begin an exciting new journey of exploration and discovery of the body you’re looking at below.
Thanks to NASA, DLR, ASI and Dawn’s international science and engineering team, we can all join the away team on the expedition to unveil Vesta’s alluring secrets.
Click the start button and watch protoplanet Vesta’s striking surface moving beneath from the perspective of Dawn flying above – in the initial survey orbit at an altitude of 2700 kilometers (1700 miles). Vesta is the second most massive object in the main asteroid belt and Dawn’s first scientific conquest.
Another video below was compiled from images taken earlier on July 24, 2011 from a higher altitude after Dawn first achieved orbit about Vesta and revealed that the northern and southern hemispheres are totally different.
The array of images in the videos was snapped by Dawn’s framing camera which was provided by the German Aerospace Center (DLR). The team then created a shape model from the images, according to Dr. Carol Raymond, Dawn’s Deputy Principal Investigator from NASA’s Jet Propulsion Laboratory in Pasadena, Calif.
The shape model will aid in studying Vesta’s strikingly diverse features of mountains, ridges, valley’s, scarps, cliffs, grooves, craters, even a ‘snowman’ and much more.
Notice that not all of Vesta is illuminated – because it’s northern winter at the asteroid. Vesta has seasons like Earth and the northern polar region in now in perpetual darkness. Data is collected over the day side and radioed back to Earth over the night side.
“On Vesta right now, the southern hemisphere is facing the sun, so everywhere between about 52 degrees north latitude and the north pole is in a long night,” says Dr. Rayman, Dawn’s Chief Engineer from JPL. “That ten percent of the surface is presently impossible to see. Because Dawn will stay in orbit around Vesta as together they travel around the sun, in 2012 it will be able to see some of this hidden scenery as the seasons advance.”
Another movie highlight is a thorough look at the gigantic south pole impact basin. The circular feature is several hundred miles wide and may have been created by a cosmic collision eons ago that excavated massive quantities of material and basically left Vesta lacking a south pole.
[/caption]
The massive feature was discovered in images taken by the Hubble Space Telescope several years ago and mission scientists have been eager to study it up close in a way that’s only possible from orbit. Dawn’s three science instruments will investigate the south pole depression in detail by collecting high resolution images and spectra which may reveal the interior composition of Vesta.
Dawn entered the survey orbit on Aug. 11 and completed seven revolutions of 69 hours each on Sept. 1. It transmitted more than 2,800 pictures from the DLR framing camera covering the entire illuminated surface and also collected over three million visible and infrared spectra from the VIR spectrometer – provided by ASI, the Italian Space Agency. This results exceeded the mission objectives.
The Dawn spacecraft is now spiraling down closer using its ion propulsion system to the next mapping orbit – known as HAMO – four times closer than the survey orbit and only some 680 km (420 miles) above the surface.
How will we work and set up a base camp on an asteroid? NASA is currently doing some field work to test technologies that could be used on future human missions to asteroids. The Desert Research And Technology Studies (D-R.A.T.S) crew is back in action, testing communication scenarios for near-Earth asteroids, and 2 new instruments from Goddard Spaceflight Center, the ExPED and VAPoR. The video shows more info.
The Orion casule in an Acoustic Chamber for testing at Lockheed Martin. Credit: Lockheed Martin
Back in 2007, when the Constellation program to return to the Moon was still the program of record for NASA, a group from Lockheed Martin began investigating how they might be able to use the Orion lunar capsule to send humans on a mission to an asteroid. Originally, this plan — called Plymouth Rock — was just a study to see how an asteroid mission with Orion could possibly serve as a complement to the baseline of Constellation’s lunar mission plans.
Now, it has turned into much more.
The Orion MPCV being built and tested at Lockheed Martin in Boulder, Colorado. Credit: John O'Connor, NASATech.net. Click for super-large, pan-able image.
Thanks to John O’Connor from NASATech.net, we are able to show you some views of the Orion MPCV inside Lockheed Martin’s facilities in Boulder, Colorado. If you click on the images, you’ll be taken to the NASATech website and extremely large versions of the images that you can pan around and see incredible details of the MPCV and the building.
After canceling Constellation in February of 2010, two months later President Obama outlined sending astronauts to a nearby asteroid by 2025 and going to Mars by the mid-2030’s.
In May of 2011, NASA confirmed that the centerpiece of those missions will be the Orion – now called the Orion MultiPurpose Crew Vehicle. The repurposed Orion lunar vehicle would now be going to an asteroid, just like Josh Hopkins and his team from Lockheed Martin envisioned in their Plymouth Rock study.
Hopkins is the Principal Investigator for Advanced Human Exploration Missions, a team of engineers who develop plans and concepts for a variety of future human exploration missions.
“Normally when you take a spacecraft or a piece of hardware that has been designed for one job and you try to figure out how to use it for a different job, you discover there are all these details that don’t work out quite right,” Hopkins told Universe Today. “But we were pleasantly surprised that when we took this lunar version of Orion and applied it to an asteroid mission, it is a really flexible and capable vehicle and a lot of the requirements for the lunar mission match pretty well with the asteroid mission.”
Concept drawing of the Plymouth Rock mission to an asteroid. Credit: Lockheed Martin.
The Plymouth Rock design called for using two specially modified Orion spacecraft docked nose to nose in order to provide enough living space, propulsion, and life-support for two astronauts heading to an asteroid. But NASA has said the MPCV will be used primarily for launch and entry while a larger habitation module would be docked to the MPCV to enable a crew of 4 to travel to deep space.
Shuttle astronaut Tom Jones was impressed with the Plymouth Rock concept, but knows a larger companion vehicle will be needed for a trip to an asteroid. “Plymouth Rock is the minimalist approach to do an asteroid mission,” he said. “That’s one way to solve the redundancy problem in the short-term.”
But even developing an in-space habitat could be a matter of repackaging things we already have. “The hab module could be derived directly from what we’ve done for space station, or it could be a commercial inflatable like from Bigelow, so that might be tried out by a commercial station or hotel in the next 10 years, so that would be demonstrated technology,” Jones said.
The Orion MPCV along with some of the people on the team that is developing and testing the capsule at the Lockheed Martin facility in Boulder, Colorado. Credit: John O'Connor, NASATech.net. Click for large, pan-able image.
“Basically the tradeoff between a larger in-space habitat module versus the dual Orion approach is that by having a separate habitat you have more living space, more storage space, and there is the potential that it would be better for performing spacewalks,” said Hopkins. “But then you have to invest the costs for developing that system.”
Hopkins added that when he and his team initially conceived the Plymouth Rock mission, they were trying to figure out how to do an asteroid mission for as little as possible. Using two Orions was cheaper than developing a module specific to an asteroid mission.
“For Plymouth Rock, we had spelled out the need to basically increase the amount of food, water, oxygen and storage in the spacecraft, and some of that is accomplished by the fact of having two spacecraft,” Hopkins said.
For now, NASA hasn’t yet changed many of the requirements for the MPCV from what they previously were for the lunar vehicle, and as the mission design evolves, so might the MPCV. But so far, the lunar design seems to be working, and Hopkins said there are several design features already in Orion that make it very capable as a deep space vehicle.
For lunar missions, Orion was designed for basically 21 days with a crew on board going from Earth to the Moon and back and having a roughly have a six month “loiter period” while the crew was down on the lunar surface. That scenario would work for an asteroid mission, as a crewed flight to an asteroid would likely be about a six-month roundtrip journey, depending on the destination.
“So in things like reliability, leak rate of atmosphere in the cabin, and protection from radiation and micrometeorites, Orion is already designed for 6-7 month missions for the hardware,” Hopkins explained. “It is just not designed to have people for that long of time period.”
Orion has solar arrays rather than fuel cells like Apollo, which enable longer missions. Another big selling point is that the MPCV is designed to be 10 times safer during ascent and entry than its predecessor, the space shuttle.
“The reentry speeds are just a little bit faster for an asteroid mission than a lunar mission,” Hopkins said, “but current the thermal protection system we have should be able to handle it.”
At look inside the hatch of the Orion capsule at the Michoud Assembly Facility near New Orleans. Credit: John O'Connor, NASATech.net. Click for large, pan-able image.
Inside the MPCV is 9 cubic meters of habitable volume. “That is not total pressurized volume of the structure, but the space that’s left after computers, seats, supplies are all accounted for,” said Hopkins. “That’s about twice the size of a modern passenger van, like a Toyota Sienna.”
One big challenge is to figure out how use every nook and cranny to package a lot of supplies in a small amount of space, as the Orion could serve as a storeroom of sorts. “We think it’s possible,” Hopkins said. “We’ve done initial calculations that we can pack a reasonable amount of volume but it would be a pretty tight fit and we also have to think about the secondary things that need to be included, so that’s work that is ongoing.”
Logistically, the Orion MPCV could even support doing an EVA from the hatch on the capsule.
“We have a hatch that is big enough that an astronaut in a space suit can get out,” Hopkins said, “and the internal systems in the spacecraft are designed to tolerate the cabin being depressurized. We don’t rely on air circulation to carry the heat away from the electronics – they have their own cold plates to take the heat away. The knobs are designed to be manipulated with spacesuit gloves on, not just bare hands. A lot of those features just worked out to be pretty applicable to the asteroid mission because it was designed for a similar set of mission requirements.”
Lockheed Martin’s Space Operations Simulation Center in Colorado can simulates the MPCV docking with an asteroid. Credit: John O'Connor, NASATech.net. Click for large, pan-able image.
Hopkins knows the requirements and capabilities the Orion, as well as the in-space habitat will likely change over time, depending on the destination and the timeline. “If the plan is to go to the moons of mars or distant asteroids relatively soon, say in the late 2020’s or early 2030s, you might go ahead and build a relatively large, capable in space habitat, because you will definitely need it for those more distant missions. But if the idea were to go to the easiest asteroids to get to and do that relatively soon, then you might stick with a smaller simpler habitat module, or perhaps even the twin Orion approach.”
When the MPCV does return from a mission to an asteroid, it will likely land in the Pacific Ocean. NASA has begun some at NASA’s Langley Research Center to certify the vehicle for water landings. Engineers have dropped a 22,000-pound MPCV mockup into the basin. The test item is similar in size and shape to MPCV, but is more rigid so it can withstand multiple drops. Each test has a different drop velocity to represent the MPCV’s possible entry conditions during water landings.
So while these tests are happening and while Hopkins and his team from Lockheed Martin are working on and testing the Orion MPCV, NASA is still trying to decide on a heavy-lift launch system capable of bringing humans beyond low Earth orbit and they have not named anyone to lead the design of a human mission to an asteroid. The NASA website doesn’t even have any official information about a human asteroid mission; it only mentions “beyond low Earth orbit” as the next stop for humans.
“We’re talking about something that is going to happen in 2025 so we haven’t even decided on a spacecraft yet,” said Michael Braukus from NASA’s Exploration Systems Mission Directorate via a phone call. “We’re planning on the asteroid mission happening; it’s just that we haven’t designated a person to be responsible for the asteroid mission itself. We have the Orion MPCV under construction and we are awaiting on the decision of a space launch system, which will be the rocket that will carry it to deep space, and we’re progressing down the road, but haven’t reached a point yet where we have actually assigned someone to start developing the mission.”
So, that appears to be NASA’s current biggest hurdle to a human asteroid mission: deciding on the Space Launch System.
You can follow Universe Today senior editor Nancy Atkinson on Twitter: @Nancy_A. Follow Universe Today for the latest space and astronomy news on Twitter @universetoday and on Facebook.
A human mission to an asteroid. Credit: Lockheed Martin
Imagine, if you can, the first time human eyes see Earth as a distant, pale blue dot. We’ve dreamed of deep space missions for centuries, and during the Apollo era, space enthusiasts assumed we’d surely be out there by now. Nevertheless, given the current state of faltering economies and potential budget cuts for NASA and other space agencies, sending humans beyond low Earth orbit might seem as impossible and unreachable as ever, if not more.
But NASA has been given a presidential directive to land astronauts on an asteroid by 2025, a mission that some say represents the most ambitious and audacious plan yet for the space agency.
“The human mission to an asteroid is an extremely important national goal,” Apollo astronaut Rusty Schweickart told Universe Today. “It will focus both NASA’s and the nation’s attention on we humans extending our capability beyond Earth/Moon space and into deep space. This is an essential capability in order to ultimately get to Mars, and a relatively short mission to a near-Earth asteroid is a logical first step in establishing a deep space human capability.”
And, Schweickart added, the excitement factor of such a mission would be off the charts. “Humans going into orbit around the Sun is pretty exciting!” said Schweickart, who piloted the lunar module during the Apollo 9 mission in 1969. “The Earth will be, for the first time to human eyes, a small blue dot.”
But not everyone agrees that an asteroid is the best destination for humans. Several of Schweickart’s Apollo compatriots, including Neil Armstrong, Jim Lovell and Gene Cernan, favor returning to the Moon and are concerned that President Obama’s directive is a “grounding of JFK’s space legacy.”
Compounding the issue is that NASA has not yet decided on a launch system capable of reaching deep space, much less started to build such a rocket.
Can NASA really go to an asteroid?
NASA Administrator Charlie Bolden has called a human mission to an asteroid “the hardest thing we can do.”
Excited by the challenge, NASA chief technology officer Bobby Braun said, “This is a risky, challenging mission. It’s the kind of mission that engineers will eat up.”
A human mission to an asteroid is a feat of technical prowess that might equal or exceed what it took for the US to reach the Moon in the 1960’s. Remember scientists who thought the moon lander might disappear into a “fluffy” lunar surface? That reflects our current understanding of asteroids: we don’t know how different asteroids are put together (rubble pile or solid surface?) and we certainly aren’t sure how to orbit and land on one.
“One of the things we need to work on is figuring out what you actually do when you get to an asteroid,” said Josh Hopkins from Lockheed Martin, who is the Principal Investigator for Advanced Human Exploration Missions. Hopkins leads a team of engineers who develop plans and concepts for a variety of future human exploration missions, including visits to asteroids. He and his team proposed the so-called “Plymouth Rock” mission to an asteroid (which we’ll discuss more in a subsequent article), and have been working on the Orion Multi-purpose Crew Vehicle (MPCV), which would be a key component of a human mission to an asteroid.
“How do you fly in formation with an asteroid that has a very weak gravitational field, so that other perturbations such as slight pressure from the Sun would affect your orbit,” Hopkins mused, in an interview with Universe Today. “How do you interact with an asteroid, especially if you don’t know exactly what its surface texture and composition is? How do you design anchors or hand-holds or tools that can dig into the surface?”
Hopkins said he and his team have been working on developing some technologies that are fairly “agnostic” about the asteroid – things that will work on a wide variety of asteroids, rather than being specific to an iron type- or carbonaceous-type asteroid.
Hypothetical astronaut mission to an asteroid. Credit: NASA Human Exploration Framework Team
A weak gravity field means astronauts probably couldn’t walk on some asteroids – they might just float away, so ideas include installing handholds or using tethers, bungees, nets or jetpacks. In order for a spaceship to stay in orbit, astronauts might have to “harpoon” the asteroid and tether it to the ship.
Hopkins said many of those types of technologies are being developed for and will be demonstrated on NASA’s OSIRIS-REx mission, the robotic sample return mission that NASA recently just selected for launch in 2016. “That mission is very complimentary to a future human mission to an asteroid,” Hopkins said.
Benefits
What benefits would a human asteroid mission provide?
“It would add to our body of knowledge about these interesting, and occasionally dangerous bodies,” said Schweickart, “and benefit our interest in protecting the Earth from asteroid impacts. So the human mission to a NEO is a very high priority in my personal list.”
Space shuttle astronaut Tom Jones says he thinks a mission to near Earth objects is a vital part of a planned human expansion into deep space. It would be an experiential stepping stone to Mars, and much more.
“Planning 6-month round trips to these ancient bodies will teach us a great deal about the early history of the solar system, how we can extract the water known to be present on certain asteroids, techniques for deflecting a future impact from an asteroid, and applying this deep space experience toward human Mars exploration,” Jones told Universe Today.
“Because an asteroid mission will not require a large, expensive lander, the cost might be comparable to a shorter, lunar mission, and NEO expeditions will certainly show we have set our sights beyond the Moon,” he said.
But Jones – and others – are concerned the Obama administration is not serious about such a mission and that the president’s rare mentions of a 2025 mission to a nearby asteroid has not led to firm NASA program plans, realistic milestones or adequate funding.
“I think 2025 is so far and so nebulous that this administration isn’t taking any responsibility for making it happen,” Jones said. “They are just going to let that slide off the table until somebody else takes over.”
Jones said he wouldn’t be surprised if nothing concrete happens with a NASA deep space mission until there is an administration change.
“The right course is to be more aggressive and say we want people out of Earth orbit in an Orion vehicle in 2020, so send them around the Moon to test out the ship, get them to the LaGrange points by 2020 and then you can start doing asteroid missions over the next few years,” Jones said. “Waiting for 2025 is just a political infinity in terms of making things happen.”
Jones said politics aside, it is certainly feasible to do all this by 2020. “That is nine years from now. My gosh, we are talking about getting a vehicle getting out of Earth orbit. If we can’t do that in nine years, we probably don’t have any hope of doing that in longer terms.”
Can NASA do such a mission? Will it happen? If so, how? Which asteroid should humans visit?
In a series of articles, we’ll take a closer look at the concepts and hurdles for a human mission to an asteroid and attempt to answer some of these questions.
3D Snowman craters and Vesta’s Equatorial Region from Dawn. This anaglyph image of Vesta's equator with the crater feature named “snowman” (center, right) was put together from two clear filter images, taken on July 24, 2011 by the framing camera instrument aboard NASA's Dawn spacecraft. The anaglyph image shows hills, troughs, ridges and steep craters. The framing camera has a resolution of about 524 yards (480 meters) per pixel. Use red-green (or red-blue) glasses to view in 3-D (left eye: red; right eye: green [or blue]). Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
[/caption]
An alien ‘Snowman’ on an alien World.
The ‘Snowman’ is a string of three craters and is among the most strange and prominent features discovered on a newly unveiled world in our solar system – the giant asteroid Vesta. It reminded team members of the jolly wintertime figure – hence its name – and is a major stand out in the 3 D image above and more snapshots below.
Until a few weeks ago, we had no idea the ‘Snowman’ even existed or what the rest of Vesta’s surface actually looked like. That is until NASA’s Dawn spacecraft approached close enough and entered orbit around Vesta on July 16 and photographed the Snowman – and other fascinating Vestan landforms.
“Each observation of Vesta is producing incredible views more exciting than the last”, says Dawn’s Chief Engineer, Dr. Marc Rayman of the Jet Propulsion Laboratory. “Every image revealed new and exotic landscapes. Vesta is unlike any other place humankind’s robotic ambassadors have visited.”
‘Snowman’ craters on Vesta. What is the origin of the ‘Snowman’?
The science team is working to determine how the ‘Snowman’ formed. This set of three craters is nicknamed ‘Snowman” and is located in the northern hemisphere of Vesta. NASA’s Dawn spacecraft obtained this image with its framing camera on August 6, 2011. This image was taken through the framing camera’s clear filter aboard the spacecraft. The framing camera has a resolution of about 280 yards (260 meters). Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
The Snowman is located in the pockmarked northern hemisphere of Vesta – see the full frame image below. The largest of the three craters is some 70 km in diameter. Altogether the trio spans roughly 120 km in length. See Image at Left
“Craters, Craters, Craters Everywhere” – that’s one thing we can now say for sure about Vesta.
And soon we’ll known a lot more about the mineralogical composition of the craters and Vesta because spectral data is now pouring in from Dawn’s spectrometers.
After being captured by Vesta, the probe “used its ion propulsion system to spiral around Vesta, gradually descending to its present altitude of 2700 kilometers (1700 miles),” says Chief Engineer Rayman. “As of Aug.11, Dawn is in its survey orbit around Vesta.”
Dawn has now begun its official science campaign. Each orbit currently last 3 days.
Dawn’s scientific Principal Investigator, Prof. Chris Russell of UCLA, fondly calls Vesta the smallest terrestrial Planet !
I asked Russell for some insight into the Snowman and how it might have formed. He outlined a few possibilities in an exclusive interview with Universe Today.
“Since there are craters, craters, craters everywhere on Vesta it is always possible that these craters struck Vesta in a nearly straight line but many years apart,” Russell replied.
“On the other hand when we see ‘coincidences’ like this, we are suspicious that it is really not a coincidence at all but that an asteroid that was a gravitational agglomerate [sometimes called a rubble pile] struck Vesta.”
“As the loosely glued together material entered Vesta’s gravity field it broke apart with the parts moving on slightly different paths. Three big pieces landed close together and made adjacent craters.”
So, which scenario is it ?
“Our science team is trying to figure this out,” Russell told me.
“They are examining the rims of the three craters to see if the rims are equally degraded, suggesting they are of similar age. They will try to see if the ejecta blankets interacted or fell separately”
“The survey data are great but maybe we will have to wait until the high altitude mapping orbit [HAMO] to get higher resolution data on the rim degradation.”
Dawn will descend to the HAMO mapping orbit in September.
Close-up View of 'Snowman' craters.
This image of the set of three craters informally nicknamed ‘Snowman’ was taken by Dawn’s framing camera on July 24, 2011 after the probe entered Vesta’s orbit. Snowman is located in the northern hemisphere of Vesta. The image was taken from a distance of about of about 3,200 miles (5,200 kilometers). The framing camera was provided by Germany. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Russell and the Dawn team are elated with the fabulous results so far, some of which have been a total surprise.
How old is the Snowman ?
“We date the age of the surface by counting the number of craters on it as a function of size and compare with a model that predicts the number of craters as a function of size and as a function of time from the present,” Russell responded.
“However this does not tell us the age of a crater. If the crater destroyed all small craters in its bowland and left a smooth layer [melt] then the small crater counts would be reset at the impact.”
“Then you could deduce the age from the crater counts. You can also check the degradation of the rim but that is not as quantitative as the small crater counts in the larger crater. The team is doing these checks but they may have to defer the final answer until they obtain the much higher resolution HAMO data,” said Russell.
Besides images, the Dawn team is also collecting spectral data as Dawn flies overhead.
“The team is mapping the surface with VIR- the Visible and Infrared Mapping Spectrometer – and will have mineral data shortly !”, Russell told me.
At the moment there is a wealth of new science data arriving from space and new missions from NASA’s Planetary Science Division are liftoff soon. Juno just launched to Jupiter, GRAIL is heading to the launch pad and lunar orbit and the Curiosity Mars Science Laboratory (MSL) is undergoing final preflight testing for blastoff to the Red Planet.
Russell had these words of encouragement to say to his fellow space explorers;
“Dawn wishes GRAIL and MSL successful launches and hopes its sister missions join her in the exploration of our solar system very shortly.”
“This year has been and continues to be a great one for Planetary Science,” Russell concluded.
Detailed 'Snowman' Crater
Dawn obtained this image with its framing camera on August 6, 2011. This image was taken through the camera’s clear filter. The camera has a resolution of about 260 meters per pixel. This image shows a detailed view of three craters, informally nicknamed 'Snowman' by the camera’s team members. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDADawn snaps First Full-Frame Image of Asteroid Vesta – Snowman at Left
NASA's Dawn spacecraft obtained this image of the giant asteroid Vesta with its framing camera on July 24, 2011. It was taken from a distance of about 3,200 miles (5,200 kilometers). Dawn entered orbit around Vesta on July 15, and will spend a year orbiting the body. The Dawn mission to Vesta and Ceres is managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif. The framing cameras were built by the Max Planck Institute for Solar System Research, Katlenburg-Lindau, Germany, and the German Aerospace Center (DLR) Institute of Planetary Research, Berlin. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
The save-the-Earth rehearsal mission Don Quijote, commissioned by the European Space Agency, is planned to test the potential of a real life-or-death mission to deflect a mass-extinction-inducing asteroid from a collision course with Earth.
Currently at ‘concept’ stage, the Don Quijote Near Earth Asteroid Impact Mitigation Mission – has been modelled on a proposed flight to either 2002 AT4 or 1989 ML, both being near-Earth asteroids, though neither represent an obvious collision risk. However, subsequent studies have proposed that Amor 2003 SM84 or even 99942 Apophis may be more suitable targets. After all, 99942 Apophis does carry a marginal (1 in 250,000) risk of an Earth impact in 2036.
Whatever the target, a dual launch of two spacecraft is proposed – an Impactor called Hidalgo (a title Cervantes gave to the original Don Quixote) and an Orbiter called Sancho (who was the Don’s faithful companion).
While the Impactor’s role is self-explanatory, the Orbiter plays a key role in interpreting the impact – the idea being to collect impact momentum and trajectory change data that would then inform future missions, in which the fate of the Earth may really be at stake.
The extent of transfer of momentum from Impactor to asteroid depends on the Impactor’s mass (just over 500 kilograms) and its velocity (about 10 kilometres a second), as well as the composition and density of the asteroid. The greatest momentum change will be achieved if the impact throws up ejecta that achieve escape velocity. If instead the Impactor just buries itself within the asteroid, not that much will be achieved, since its mass will be substantially less than any mass-extinction-inducing asteroid. For example, the object that created the Chicxulub crater and wiped out the dinosaurs (yes, alright – except for the birds) is thought to have been in the order of 10 kilometres in diameter.
So before the impact, to assist future targeting and required impact velocity calculations, the Orbiter will make a detailed analysis of the target asteroid’s overall mass and its near-surface density and granularity. Then, after the impact, the Orbiter will assess the speed and distribution of the collision ejecta via its Impact Camera.
However, accurately measuring the degree of deflection achieved by the impact represents a substantial challenge for the mission. We will need much better data about the target asteroid’s mass and velocity than we can establish from Earth. So, the Orbiter will do a series of fly-bys and then go into orbit around the asteroid to assess how much the asteroid is affected by the spacecraft’s proximity.
A precise determination of the Orbiter’s distance from the asteroid will be achieved by its Laser Altimeter, while a Radio Science Experiment will precisely determine the Orbiter’s position (and hence the asteroid’s position) relative to the Earth.
Having then established the Orbiter as a reference point, the effect of the collision of the Impactor will be assessed. However, a significant confounding factor is the Yarkovsky effect – the effect of solar heating of the asteroid, which induces the emission of thermal photons and hence generates a tiny amount of thrust. The Yarkovsky effect naturally pushes an asteroid’s orbit outwards if it has a prograde spin (in the direction of its orbit) – or inwards if it has retrograde spin. Hence, the Orbiter will also need a Thermal Infrared Spectrometer to separate the Yarkovsky effect from the effect of the impact.
To estimate the effect of Hidalgo's collision, the Yarkovsky effect must be acounted for. Heating of an asteroid's surface by the Sun causes thermal radiation. The nett cumulative momentum of that radiation is from surfaces that have just turned out of the Sun's light (i.e. 'dusk'). In asteroids with prograde spin, this will push the asteroid into a higher orbit - i.e. further away from the Sun. But, for asteroids with retrograde rotation, the orbit decays - i.e. towards the Sun.
And of course, given the importance of the Orbiter as a reference point, the effect of solar radiation on it must also be measured. Indeed, we will also need to factor in that this effect will change as the shiny new spacecraft’s highly-reflective surfaces lose their sheen. Highly reflective surfaces will emit radiation, almost immediately, at energy levels (i.e. high momentum) almost equivalent to the incident radiation. However, low albedo surfaces may only release lower energy (i.e. lower momentum) thermal radiation – and will do so more slowly.
To put it another way, a mirror surface makes a much better solar sail than a black surface.
So in a nutshell, the Don Quijote impact mitigation mission will require an Impactor with a Targeting Camera – and an Orbiter with an Impact Observation Camera, a Laser Altimeter, a Radio Science Experiment and a Thermal Infrared Spectrometer – and you should remember to measure the effect of solar radiation pressure on the spacecraft early in the mission, when it’s shiny – and later on, when it’s not.
Barringer Crater, also known as Meteor Crater, in Arizona. This crater was formed around 50,000 years ago by the impact of a nickel-iron meteorite. Near the top of the image, the visitors center, complete with tour buses on the parking lot, provides a sense of scale. Credit: National Map Seamless Viewer/US Geological Service
Is the Earth more likely or less likely to be hit by an asteroid or comet now as compared to, say, 20 million years ago? Several studies have claimed to have found periodic variations, with the probability of giant impacts increasing and decreasing in a regular pattern. Now a new analysis by Coryn Bailer-Jones from the Max Planck Institute for Astronomy (MPIA), published in the Monthly Notes of the Royal Astronomical Society, shows those simple periodic patterns to be statistical artifacts. His results indicate either that the Earth is as likely to suffer a major impact now as it was in the past, or that there has been a slight increase impact rate events over the past 250 million years.
The results also lay to rest the idea of the existence of an as-yet undetected companion star to the Sun, dubbed “Nemesis.”
Giant impacts by comets or asteroids have been linked to several mass extinction events on Earth, most famously to the demise of the dinosaurs 65 million years ago. Nearly 200 identifiable craters on the Earth’s surface, some of them hundreds of kilometers in diameter, bear witness to these catastrophic collisions.
Understanding the way impact rates might have varied over time is not just an academic question. It is an important ingredient when scientists estimate the risk Earth currently faces from catastrophic cosmic impacts.
Since the mid-1980s, a number of authors have claimed to have identified periodic variations in the impact rate. Using crater data, notably the age estimates for the different craters, they derive a regular pattern where, every so-and-so-many million years (values vary between 13 and 50 million years), an era with fewer impacts is followed by an era with increased impact activity, and so on.
One proposed mechanism for these variations is the periodic motion of our Solar System relative to the main plane of the Milky Way Galaxy. This could lead to differences in the way that the minute gravitational influence of nearby stars tugs on the objects in the Oort cloud, a giant repository of comets that forms a shell around the outer Solar System, nearly a light-year away from the Sun, leading to episodes in which more comets than usual leave the Oort cloud to make their way into the inner Solar System – and, potentially, towards a collision with the Earth. A more spectacular proposal posits the existence of an as-yet undetected companion star to the Sun, dubbed “Nemesis”. Its highly elongated orbit, the reasoning goes, would periodically bring Nemesis closer to the Oort cloud, again triggering an increase in the number of comets setting course for Earth.
For MPIA’s Coryn-Bailer-Jones, these results are evidence not of undiscovered cosmic phenomena, but of subtle pitfalls of traditional (“frequentist”) statistical reasoning. Bailer-Jones: “There is a tendency for people to find patterns in nature that do not exist. Unfortunately, in certain situations traditional statistics plays to that particular weakness.”
That is why, for his analysis, Bailer-Jones chose an alternative way of evaluating probabilities (“Bayesian statistics”), which avoids many of the pitfalls that hamper the traditional analysis of impact crater data. He found that simple periodic variations can be confidently ruled out. Instead, there is a general trend: From about 250 million years ago to the present, the impact rate, as judged by the number of craters of different ages, increases steadily.
There are two possible explanations for this trend. Smaller craters erode more easily, and older craters have had more time to erode away. The trend could simply reflect the fact that larger, younger craters are easier for us to find than smaller, older ones. “If we look only at craters larger than 35 km and younger than 400 million years, which are less affected by erosion and infilling, we find no such trend,” Bailer-Jones explains.
On the other hand, at least part of the increasing impact rate could be real. In fact, there are analyses of impact craters on the Moon, where there are no natural geological processes leading to infilling and erosion of craters, that point towards just such a trend.
Whatever the reason for the trend, simple periodic variations such as those caused by Nemesis are laid to rest by Bailer-Jones’ results. “From the crater record there is no evidence for Nemesis. What remains is the intriguing question of whether or not impacts have become ever more frequent over the past 250 million years,” he concludes.
2010 TK7 is seen as a speck of light in the center of this image, which is the addition of three individual exposures taken with the MegaCam camera at CFHT. The telescope was tracking the motion of the asteroid, leading to the image of the stars to be trailed. With three exposures added, stars end up looking like a broken trail. Credit: C. Veillet, Canada-France-Hawaii Telescope.
[/caption]
The first known “Trojan” asteroid in Earth’s orbit has been discovered. A Trojan asteroid shares an orbit with a larger planet or moon, but does not collide with it because it orbits around one of two Lagrangian points. Trojans sharing an orbit with Earth have been predicted but never found until now. Astronomers analyzing data from the asteroid-hunting WISE telescope – which ceased operations in February 2011 – found the asteroid, named 2010 TK7, and followup observations with the Canada-France-Hawaii Telescope on Mauna Kea in Hawaii confirmed the discovery and the object’s stealthy orbit.
In our solar system, we know of Trojans that share orbits with Neptune, Mars and Jupiter. Two of Saturn’s moons share orbits with Trojans. Astronomers have known that Earth Trojans would be difficult to find because they are relatively small and appear near the sun from Earth’s point of view.
But 2010 TK7 proves that Trojans associated to Earth can be found, and astronomers predict that since one has been found, perhaps they’ll find more, as we’ll learn more about their dynamics and characteristics of their population from this first one.
“These asteroids dwell mostly in the daylight, making them very hard to see,” said Martin Connors of Athabasca University in Canada, lead author of a new paper on the discovery in the July 28 issue of the journal Nature. “But we finally found one, because the object has an unusual orbit that takes it farther away from the sun than what is typical for Trojans. WISE was a game-changer, giving us a point of view difficult to have at Earth’s surface.”
The animation below shows the orbit of 2010 TK7 (green dots).
The asteroid is roughly 1,000 feet (300 meters) in diameter. It has an unusual orbit that traces a complex motion near the L4 point. However, the asteroid also moves above and below the plane. The object is about 50 million miles (80 million kilometers) from Earth. The asteroid’s orbit is well-defined and for at least the next 100 years, it will not come closer to Earth than 15 million miles (24 million kilometers).
“It’s as though Earth is playing follow the leader,” said Amy Mainzer, the principal investigator of WISE’s extended mission called NEOWISE that looked especially for Near Earth Object “Earth always is chasing this asteroid around.”
Asteroid 2010 TK7 is circled in green, in this single frame taken by NASA's Wide-field Infrared Survey Explorer, or WISE. Image credit: NASA/JPL-Caltech/UCLA
A handful of other asteroids also have orbits similar to Earth. Such objects could make excellent candidates for future robotic or human exploration. Asteroid 2010 TK7 is not a good target because it travels too far above and below the plane of Earth’s orbit, which would require large amounts of fuel to reach it.
“This observation illustrates why NASA’s NEO Observation program funded the mission enhancement to process data collected by WISE,” said Lindley Johnson, NEOWISE program executive at NASA Headquarters in Washington. “We believed there was great potential to find objects in near-Earth space that had not been seen before.”
The WISE telescope scanned the entire sky in infrared light from January 2010 to February 2011. The NEOWISE project observed more than 155,000 asteroids in the main belt between Mars and Jupiter, and more than 500 NEOs, discovering 132 that were previously unknown.
Enhanced Image of Vesta Captured by Dawn on July 9, 2011. NASA's Dawn spacecraft entered orbit around Vesta on July 16, 2011. Dawn obtained the raw image of Vesta with its framing camera on July 9, 2011 - which has been enhanced and annotated. It was taken from a distance of about 26,000 miles (41,000 kilometers) away from the protoplanet Vesta. Each pixel in the image corresponds to roughly 2.4 miles (3.8 kilometers). Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA. Enhanced and annotated by Ken Kremer
[/caption]
NASA’s super exciting Dawn mission to the Asteroid Belt marked a major milestone in human history by becoming the first ever spacecraft from Planet Earth to achieve orbit around a Protoplanet – Vesta – on July 16. Dawn was launched in September 2007 and was 117 million miles (188 million km) distant from Earth as it was captured by Asteroid Vesta.
Dawn’s achievements thus far have already exceeded the wildest expectations of the science and engineering teams, and the adventure has only just begun ! – so say Dawn’s Science Principal Investigator Prof. Chris Russell, Chief Engineer Dr. Marc Rayman (think Scotty !) and NASA’s Planetary Science Director Jim Green in exclusive new interviews with Universe Today.
As you read these words, Dawn is steadily unveiling new Vesta vistas never before seen by a human being – and in ever higher resolution. And it’s only made possible via the revolutionary and exotic ion propulsion thrusters propelling Dawn through space (think Star Trek !). That’s what NASA, science and space exploration are all about.
“Dawn is in orbit, remains in good health and is continuing to perform all of its functions,” Marc Rayman of the Jet Propulsion Laboratory, Pasadena, Calif., told me. “Indeed, that is how we know it achieved orbit. The confirmation received in a routine communications session that it has continued thrusting is all we needed.”
Image of Vesta Captured by Dawn on July 9, 2011. NASA's Dawn spacecraft obtained this image with its framing camera on July 9, 2011. It was taken from a distance of about 26,000 miles (41,000 kilometers) away from the protoplanet Vesta. Each pixel in the image corresponds to roughly 2.4 miles (3.8 kilometers). Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Dawn entered orbit at about 9900 miles (16000 km) altitude after a nearly 4 year journey of 1.73 billion miles.
Over the next few weeks, the spacecrafts primary task is to gradually spiral down to its initial science operations orbit, approximately 1700 miles above the pock marked surface.
Vesta is the second most massive object in the main Asteroid Belt between Mars and Jupiter. Dawn is the first probe to orbit an object in the Asteroid Belt.
I asked Principal Investigator Chris Russell from UCLA for a status update on Dawn and to describe what the team can conclude from the images and data collected thus far.
“The Dawn team is really, really excited right now,” Russell replied.
“This is what we have been planning now for over a decade and to finally be in orbit around our first ‘protoplanet’ is fantastic.”
“The images exceed my wildest dreams. The terrain both shows the stress on the Vestan surface exerted by 4.5 billion years of collisions while preserving evidence [it seems] of what may be internal processes. The result is a complex surface that is very interesting and should be very scientifically productive.”
NASA's Dawn spacecraft, illustrated in this artist's concept, is propelled by ion engines to Protoplanets Vesta and Ceres. Credit: NASA/JPL
“The team is looking at our low resolution images and trying to make preliminary assessments but the final answers await the higher resolution data that is still to come.”
Russell praised the team and described how well the spacecraft was operating.
“The flight team has been great on this project and deserves a lot of credit for getting us to Vesta EARLY and giving us much more observation time than we had planned,” Russell told me.
“And they have kept the spacecraft healthy and the instruments safe. Now we are ready to work in earnest on our science observations.”
Dawn will remain in orbit at Vesta for one year. Then it will fire its ion thrusters and head for the Dwarf Planet Ceres – the largest object in the Asteroid Belt. Dawn will then achieve another major milestone and become the first spacecraft ever to orbit two celestial objects.
Dawn launch on September 27, 2007 by a Delta II rocket from Cape Canaveral Air Force Station, Florida. Credit: Ken Kremer
Jim Green, Director of Planetary Science for the Science Mission Directorate (SMD) at NASA HQ in Washington, DC, summed up his feelings about Dawn in this way;
“Getting Dawn into orbit is an amazing achievement,” Green told me.
“Instead of the ‘fire the thrusters full blast’ we just sort of slid into orbit letting gravity grab the spacecraft with a light tug. This gives us great confidence that the big challenge down the road of getting into orbit around Ceres can also be accomplished just as easily.”
Sharper new images from Vesta will be published by NASA in the next day or so.
“We did take a few navigation images in this last sequence and when they get through processing they should be put on the web this week,” Russell informed. “These images are from a similar angle to the last set and with somewhat better resolution and will not reveal much new.”
However, since Dawn is now orbiting Vesta our upcoming view of the protoplanet will be quite different from what we’ve seen in the approach images thus far.
“We will be changing views in the future as the spacecraft begins to climb into its science orbit,” stated Russell.
“This may reveal new features on the surface as well as giving us better resolution. So stay tuned.”
Marc Rayman explained how and why Dawn’s trajectory is changing from equatorial to polar:
“Now that we are close enough to Vesta for its gravity to cause a significant curvature in the trajectory, our view is beginning to change,” said Rayman. “That will be evident in the pictures taken now and in the near future, as the spacecraft arcs north over the dark side and then orbits back to the south over the illuminated side.”
“The sun is over the southern hemisphere right now,” added Russell. “When we leave we are hoping to see it shine in the north.”
Dawn is an international mission with significant participation from Germany and Italy. The navigation images were taken by Dawn’s framing cameras which were built in Germany.
Exploring Vesta is like studying a fossil from the distant past that will immeasurably increase our knowledge of the beginnings of our solar system and how it evolved over time.
Dawn Infographic Poster - click to enlarge. Credit: NASA
Vesta suffered a cosmic collision at the south pole in the distant past that Dawn can now study at close range.
“For now we are viewing a fantastic asteroid, seeing it up close as we zero in on its southern hemisphere, looking at the huge central peak, and wondering how it got there,” explained Jim Green
“We know Vesta was nearly spherical at one time. Then a collision in its southern hemisphere occurred blowing off an enormous amount of material where a central peak now remains.”
That intriguing peak is now obvious in the latest Dawn images from Vesta. But what does it mean and reveal ?
“We wonder what is that peak? replied Green. “Is it part of the core exposed?
“Was it formed as a result of the impact or did it arise from volcanic action?”
“The Dawn team hopes to answer these questions. I can’t wait!” Green told me.
As a result of that ancient south pole collision, about 5% of all the meteorites found on Earth actually originate from Vesta.
Keep your eyes glued to Dawn as mysterious Vesta’s alluring secrets are unveiled.
Dawn Trajectory and Current Location in orbit at Vesta on July 18, 2011. Credit: NASA/JPL
NASA's Dawn spacecraft obtained this image of the giant asteroid Vesta with its framing camera on July 9, 2011. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
[/caption]
As we anticipate the Dawn spacecraft going into orbit of Vesta within the next 36 hours, here’s the latest image taken as the spacecraft approaches Vesta, taken on July 9 from a distance of about 41,000 kilometers (26,000 miles). Surface details are coming into focus a little more than from the previous image that was released. The Dawn mission is exciting, as it will be the first spacecraft to enter orbit around a main-belt asteroid, and as we’ve said before, it will be intriguing for scientists to study this lumpy little world in detail and perhaps figuring out what Vesta really is.
Below is an “enhanced” look at this view of Vesta by Stu Atkinson.
Some astronomers classify Vesta as an asteroid, some a protoplanet, and some are on the fence. It’s not really considered a dwarf planet, but the classification could be re-evaluated when Dawn gets in orbit of Vesta and studies it in detail.
An enhanced view of Vesta from the July 9, 2011 image taken by the Dawn spacecraft. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA, enhancements by Stu Atkinson.
Stu sent us this image with the caveat that he created it for his own amusement/entertainment, and that it’s not a scientifically enhanced image — i.e., it’s not to be 100% relied upon for feature identification, etc. But it’s a little clearer and sharper than the original from NASA/JPL. Thanks Stu!
Engineers expect the spacecraft to be captured into orbit at approximately 10 p.m. PDT Friday, July 15 (1 a.m. EDT Saturday, July 16). They expect to hear from the spacecraft and confirm that it performed as planned during a scheduled communications pass that starts at approximately 11:30 p.m. PDT on Saturday, July 16 (2:30 a.m. EDT Sunday, July 17). When Vesta captures Dawn into its orbit, engineers estimate there will be approximately 9,900 miles (16,000 kilometers) between the spacecraft and Vesta. At that point, the two will be approximately 117 million miles (188 million kilometers) from Earth.
“It has taken nearly four years to get to this point,” said Robert Mase, Dawn project manager at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “Our latest tests and check-outs show that Dawn is right on target and performing normally.”
Engineers have been subtly shaping Dawn’s trajectory for years to match Vesta’s orbit around the sun with its ion engine. Unlike other missions, where dramatic propulsive burns put spacecraft into orbit around a planet, Dawn will ease up next to Vesta. Then the asteroid’s gravity will capture the spacecraft into orbit. However, until Dawn nears Vesta and makes accurate measurements, the asteroid’s mass and gravity will only be estimates. So the Dawn team will need a few days to refine the exact moment of orbit capture.
Launched in September 2007, Dawn will depart for its second destination, the dwarf planet Ceres, in July 2012. The spacecraft will be the first to orbit two bodies in our solar system.
Stay tuned for more details and updates on the Dawn mission.
