Asteroid close pass highlights need to investigate NEAs via NASA missions
Following 2012 DA14′s close pass to Earth on Friday, asteroids once again found their way into the general public’s consciousness. 2012 DA14 was not – as Hollywood movies like to depict – a giant planet killer, but it did highlight NASA’s interest in learning more about Near Earth Asteroids (NEA), which includes sending humans out to visit them in deep space.
Big Day for Space Rocks:
The arrival of 2012 DA14 was predicted well in advance and was never a threat to the planet. However, Friday began with news from Russia of a space rock – just a few metres across – exploding in Earths atmosphere above the city of Chelyabinsk, Russia at about 03:15 UTC.
Numerous videos began to surface on the internet, showing a fireball and explosion consistent with a meteor up to a few metres in size exploding in the atmosphere, possibly several kilometers in the sky.
The resulting shockwave caused significant damage on the ground, shattering windows and blowing in doors – causing injuries to several hundred people.
NASA and ESA were fast to claim the meteor was unlikely to be related to 2012 DA14.
“Current information, which is not yet complete nor confirmed, points to a small asteroid,” said Detlef Koschny, Head of Near-Earth Object activity at ESAs Space Situational Awareness (SSA) programme office.
“There is no way it could have been predicted with the technical means available today. What can be said with near certainty is that this object has no connection with asteroid 2012 DA14.”
Asteroid 2012 DA14 made its predicted closest approach to Earth at 19:27 UTC, making a close flyby of the planet at a distance of 17,150 miles (27,600 kilometers) above Earth’s surface. The distance was closer to Earth than the orbit of the fleet of satellites in Geostationary orbit – however, none were in any danger of being impacted by the asteroid.
The path of 2012 DA14 was well understood thanks to NASA Near Earth Object Observation (NEOO) Program, which detects and tracks asteroids and comets passing close to Earth using ground and space-based telescopes.
The network of projects supported by this program, commonly called “Spaceguard,” discovers these objects, characterizes a subset of them and plots their orbits to determine if any could be potentially hazardous to our planet.
Objects of interest can also have their orbits predicted around 100 years into the future, with 2012 DA14 set to make two more close passes over this timeframe – neither of which are expected to threaten Earth.
The Near-Earth Object Program Office at JPL manages the technical and scientific activities for the NEOO Program and performs more precise orbit determination on the objects, predicting whether any will become an impact hazard to the Earth, or any other planet in the solar system.
While the close pass allowed astronomers to take a close look at the asteroid, scientists at NASA’s Goldstone radar dish in the Mojave Desert have been observing 2012 DA14 in great detail as it passed, collating information about its surface features and composition.
Getting Up Close and Personal:
Via the drive need to learn more about Near Earth Asteroids, NASA teams continue to build a potential roadmap involving robotic, followed by human, missions to reach out and touch one an asteroid as it hurtles through space.
On the robotic side, the upcoming OSIRIS-REx planetary science mission is aiming to return a sample of the carbonaceous asteroid 1999 RQ36. The mission – launching in 2016 – has a target of returning the asteroid sample to Earth in 2023.
Following launch, OSIRIS-REx will take four years to approach the primitive NEA. Once within three miles of the asteroid, the spacecraft will begin six months of comprehensive surface mapping.
The science team then will pick a location from where the spacecraft’s arm will take a sample, allowing the spacecraft to gradually move closer to the site for the arm to extend to collect more than two ounces of material for return to Earth in 2023.
RQ36 is approximately 1,900 feet in diameter and has hardly altered over time – thus it is likely to represent a snapshot of our solar systems infancy. The asteroid is likely rich in carbon, a key element in the organic molecules necessary for life.
Organic molecules have been found in meteorite and comet samples, indicating some of lifes ingredients can be created in space. Scientists want to see if they also are present on RQ36.
Also, the mission will accurately measure the “Yarkovsky effect” for the first time. The effect is a small push caused by the sun on an asteroid as it absorbs sunlight and re-emits that energy as heat. The small push adds up over time, but it is uneven due to an asteroids shape, wobble, surface composition and rotation.
For scientists to predict an Earth-approaching asteroids path, they must understand how the effect will change its orbit. OSIRIS-REx will help refine RQ36′s orbit to ascertain its trajectory and devise future strategies to mitigate possible Earth impacts from celestial objects.
On the return journey, the sample will be stored in a capsule for the long trip back to Earth, ahead of re-entry and a landing at Utahs Test and Training Range – where the Orion parachute testing is currently taking place – in 2023.
As far as sending humans to a NEA, that is the plan, although it remains undefined.
Technically, a lot of work has been completed on the baseline for a mission to a NEA, not least the options for how the mission would be conducted once at the asteroid.
However, a preferred plan – and indeed a destination – remains illusive, with only notional examples for missions that would take place no sooner than the middle of the next decade.
There is no need to rush towards a full outline, not least because such a mission is so many years away, although NASA recently explained the complex nature of at least selecting which asteroid to visit and the challenges of sending a crew safely there and back.
“Because there are thousands of known NEAs, and likely many more to be discovered, one of the first challenges of a NEA mission is choosing the ideal destination,” noted a public exploration overview presentation.
“Distance is another challenge. Although some NEAs pass close to Earth, even within the Moon’s orbit, larger and more interesting NEA destinations may be tens of millions of miles away.
“To reach these NEAs, astronauts would have to travel about six months for a round trip, which is a long time to go without a resupply of water, food, or air longer than has ever been attempted in space.”
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To date, the only notional targets have been revealed, such as those in the “Flexible Approach” presentation (available on L2 -LINK), created after the Augustine Commission’s review into NASA’s Human Space Flight activities. This presentation continues to be the most expansive human exploration roadmap to be created in recent years.
A mission to Near Earth Object 1999AO10, requiring a mission launch date of January 2, 2026, is the first case example examined by the NASA authored study.
The NEO 1999AO10 deep space mission would last 155 days, around half of the mission length for the alternative candidate mentioned in the Flexible Path approach – 304 days – for a mission to NEO 2001 GP2.
How to get both the crew and the considerable amount of hardware to a NEA destination is also still under evaluation, with multi-launch SLS campaigns the baseline approach, and the use of an Exploration Platform or Gateway – as the centerpiece of several exploration pathways – as the main alternative.
This alternative relates to a Gateway that would be built at the International Space Station (ISS) and then sent to Earth Moon Lagrange point (EML2) via Solar Electric Propulsion (SEP). This Gateway would provide a staging post for missions to the Lunar Surface, NEAs, Mars and potentially other destinations.
The internal evaluations into NASA’s exploration path are understood to be complete to a preliminary level. However, there is no news on making such a roadmap public, not least with the threat of large scale NASA funding cuts at the political level hanging over the Agency’s head.
Some reasonably expansive ideas for NEA specific missions include Boeing’s conceptual approach involving the EML2 Gateway at last year’s Global Exploration Workshop.
Under this Boeing plan, Solar Electric Propulsion would be used by NASA for NEA missions – a technology also cited by Aerojet as a viable solution.
This new propulsion system would be gradually developed over the next 10 years, although a demonstration flight would be capable of readiness by 2014.
A NASA docking system, Spacecraft boom, triple panel SEP module, Solar Array mast, and Alpha-joint (similar to the ISS’ Beta joint) would be developed between 2016 and 2020 – all leading to the creation of a 320 kW SEP operational spacecraft for NEA missions by 2022.
Under the Boeing notional plan, a 2024 NEA mission to NEA2008EV5 would depart not from Earth, but from the ISS-EP at the Earth-Moon L2 (EML2) point.
Using the new SEP technology, transit from the EML2 point to the NEA of interest would take approximately 100 days with SLS’ third stage used to “kick start” the stage and shorten the trip. SLS would be involved with the Gateway plan.
Investigations at the NEA would last for approximately 30 days before a ~235-day trip back to Earth for a total mission duration of roughly one year.
Boeing also produced new outline presentations that focused on crewed Lunar Surface and Mars missions, effectively providing a full roadmap to follow on from NASA’s human test flight, Exploration Mission -2 (EM-2).
However, such proposals would require inclusion in NASA’s Design Reference Mission (DRM) documentation to become part of the Agency’s official plans.
A large amount of simulation work has already taken place, mainly via the NEEMO (NASA Extreme Environment Mission Operations) efforts off the coast of Florida. These missions practiced protocols, communication delays and simulations involving former NASA astronauts at the at the Aquarius underwater habitat.
Back at the Johnson Space Center (JSC) documentation has been created on potential mission scenarios, including EVAs to the surface of an asteroid.
(Images: L2 Content, NASA and Boeing)
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