Kepler team investigating promising method to continue exoplanet searches

Earlier this year the Kepler orbiting observatory lost the ability to point its telescope with the precision necessary to continue its search for exoplanets as it has done since 2009. With just two reaction wheels working, it was thought that the science with the spacecraft would be extremely limited and probably not involving exoplanets.

However, the Kepler team has come up with Plan B that looks very promising:

A Sunny Outlook for NASA Kepler’s Second Light

You may have thought that NASA’s Kepler spacecraft was finished. Well, think again. A repurposed Kepler Space telescope may soon start searching the sky again.

A new mission concept, dubbed K2, would continue Kepler’s search for other worlds, and introduce new opportunities to observe star clusters, young and old stars, active galaxies and supernovae.

In May, the Kepler spacecraft lost the second of four gyroscope-like reaction wheels, which are used to precisely point the spacecraft, ending new data collection for the original mission. The spacecraft required three functioning wheels to maintain the precision pointing necessary to detect the signal of small Earth-sized exoplanets, which are planets outside our solar system, orbiting stars like our sun in what’s known as the habitable zone — the range of distances from a star where the surface temperature of a planet might be suitable for liquid water.

With the failure of a second reaction wheel, the spacecraft can no longer precisely point at the mission’s original field of view. The culprit is none other than our own sun.

The very body that provides Kepler with its energy needs also pushes the spacecraft around by the pressure exerted when the photons of sunlight strike the spacecraft. Without a third wheel to help counteract the solar pressure, the spacecraft’s ultra-precise pointing capability cannot be controlled in all directions.

However, Kepler mission and Ball Aerospace engineers have developed an innovative way of recovering pointing stability by maneuvering the spacecraft so that the solar pressure is evenly distributed across the surfaces of the spacecraft.

To achieve this level of stability, the orientation of the spacecraft must be nearly parallel to its orbital path around the sun, which is slightly offset from the ecliptic, the orbital plane of Earth. The ecliptic plane defines the band of sky in which lie the constellations of the zodiac.

This technique of using the sun as the ‘third wheel’ to control pointing is currently being tested on the spacecraft and early results are already coming in. During a pointing performance test in late October, a full frame image of the space telescope’s full field of view was captured showing part of the constellation Sagittarius.

Photons of light from a distant star field were collected over a 30-minute period and produced an image quality within five percent of the primary mission image quality, which used four reaction wheels to control pointing stability. Additional testing is underway to demonstrate the ability to maintain this level of pointing control for days and weeks.

To capture the telltale signature of a distant planet as it crosses the face of its host star and temporarily blocks the amount of starlight collected by Kepler, the spacecraft must maintain pointing stability over these longer periods.

“This ‘second light’ image provides a successful first step in a process that may yet result in new observations and continued discoveries from the Kepler space telescope,” said Charlie Sobeck, Kepler deputy project manager at NASA Ames Research Center in Moffett Field, CA.

The K2 mission concept has been presented to NASA Headquarters. A decision to proceed to the 2014 Senior Review – a biannual assessment of operating missions – and propose for budget to fly K2 is expected by the end of 2013.

Kepler’s original mission, which is still in progress to fully process the wealth of data collected, is to determine what percentage of stars like the sun harbor small planets the approximate size and surface temperature of Earth. For four years, the space telescope simultaneously and continuously monitored the brightness of more than 150,000 stars, recording a measurement every 30 minutes.

More than a year of the data collected by Kepler remains to be fully reviewed and analyzed.

Kepler's Second Light: How K2 Will Work
This conception illustration depicts how solar pressure can be used to
balance NASA’s Kepler spacecraft, keeping the telescope stable enough
to continue searching for transiting planets around distant stars.
Image Credit: NASA Ames/W Stenzel


The Year in Space – desk and wall calendars

With the starting gun about to fire for Christmas gift shopping, here are a couple of suggestions. As I’ve come to do every year, I’m endorsing The Year In Space Desk Calendar and Year In Space Wall Calendar. My wife has used here space desk calendar for years and years and I have the wall calendar in my studio.


The Desk Calendar contains

  • 53 full-page weekly calendars
  • 16 half-page monthly calendars
  • 2 full-year planning calendars
  • 1 four-year long-range calendar
  • Daily Moon-phase calendars

The  Wall Calendar is a joint project with the Planetary Society. Each month displays a big array of beautiful images and contains lots of interesting information on a wide array of space topics.



The Year In Space Wall Calendar was named “Science Geek Gift of the Year” by MSNBC’s Cosmic Log website.

Video: NOVA’s “Asteroid: Doomsday or Payday” + Background on the Chelyabinsk research

Sandia National Laboratories released this item about work done by one of its researchers on the Chelyabinsk meteor fireball. His work was included in a recent NOVA episode Asteroid: Doomsday or Payday.

Physicist’s journey reveals smaller asteroids could cause bigger problems

ALBUQUERQUE, N.M. — Once in a lifetime, a physicist may get a chance to test his theories and simulations in a real-life event that changes the course of his scientific life. But rarely does that opportunity literally fall from the sky.

Chelyabinsk sky rendering

The asteroid that fell to earth near Chelyabinsk, Russia, 
gave scientists new insights into the risks of  smaller
asteroid impacts. (Simulation by Mark Boslough;

rendering by Brad Carvey.) 

That’s the impact of the Feb. 15 asteroid that burst over the Russian city of Chelyabinsk on Sandia physicist Mark Boslough, subject of a TV documentary that airs tonight and co-author of a recent cover story in Nature about the asteroid fireball that injured about 1,500 people and damaged more than 7,000 buildings, collapsing roofs and breaking thousands of windows.

Boslough’s journey to Russia shortly after the impact is chronicled in the NOVA episode “Asteroid: Doomsday or Payday,” which will air on Public Broadcasting Service stations [on Nov. 20, 2013].

The complete NOVA program Asteroid; Doomsday or Payday.

The show focuses on the destructive potential of asteroids, chronicling how Boslough and his colleagues learn that small asteroids can do far more damage than previously thought. The Nature paper also suggests that there may be more small asteroids than formerly thought.

The day the asteroid hit, Boslough learned of the event via Facebook from posts of Russian news stories and YouTube videos showing an object that exploded in the Russian sky.

“I saw it on Facebook long before the sound wave had even arrived in this part of the world,” Boslough said, estimating the transglobal sound wave took more than seven hours to reach New Mexico. “I really didn’t expect to experience this in my lifetime.”

As one of the first scientists to visit Chelyabinsk after the asteroid struck, Boslough set out to discover where the object came from. Because it came down near a populated area, he and his colleagues were able to collect videos from people who caught the asteroid on film and video, especially the ubiquitous Russian dashboard cameras, a staple in establishing blame in traffic mishaps.

“This event was certainly one of the best-documented asteroid events ever,” said Boslough.

Boslough’s goal was to perform stellar calculations of the asteroid’s trajectory by visiting — at night when the stars shone — the exact spots where the footage was recorded.

“If the stars show up on the digital camera, we can get those angles and then calibrate that image that was taken from the dash cam, and know exactly the angles to the trajectory of the fireball,” he said in the documentary. “We’ll have a very precise trajectory as it streaked through the atmosphere, so we can backtrack that to get the orbit, the pre-impact orbit.”

The program also discusses how asteroids can contain rare and valuable elements, leading researchers to seriously evaluate the benefit of harvesting them for their rare elements.

But Boslough also wants the research community to pay more attention to the potential risk that asteroids present.

“If something like the Tunguska event of 1908 happened now, it could kill hundreds of thousands or even a million people, if it happened right over a big city,” he said in the documentary. “An asteroid has more damage potential on the ground than a nuclear bomb of the same energy.”

Boslough was part of a team of 33 researchers who completed the study featured in Nature. “A 500-kiloton airburst over Chelyabinsk and an enhanced hazard from small impactors” examines the characteristics of the fireball. Boslough and his colleagues also used the simulations to help design the journal’s cover.

You also can see an animated simulation of the airburst produced by Boslough, as well as scientific animations and images by Sandia contractor and visual effect expert Brad Carvey and visual effect expert Andrea Carvey. Sandia’s Laboratory Directed Research & Development program funded the simulations.

Using data collected from his visit shortly after the asteroid struck, along with data from an international team, Boslough developed several additional simulations that he and other researchers have used to model the explosion and estimate the force of the blast.

The paper’s authors performed a global survey of airbursts of a kiloton or more and found that the number of building-sized objects may be 10 times greater than estimates based on other methods.

The authors, led by Peter Brown of the University of Western Ontario, estimated the Chelyabinsk event was equivalent to an explosion of about 500 kilotons of TNT. At its peak, the airburst appeared to be 30 times brighter than the sun.

“Because the frequency of a strike of an asteroid of this size has exceeded expectations, with three such strikes in just over a century (Chelyabinsk, Tunguska and a large airburst in the South Atlantic in 1963 detected by infrasound), the number of similar-sized asteroids capable of causing damage may be greater than suspected,” Boslough said.

Dick Spalding of Sandia’s Nonproliferation Technologies Research and Development Department also co-authored the paper.

The authors also showed that previous models for estimating airburst damage do not match the observations.

An earlier paper by Boslough highlights the conclusion that most airbursts are more damaging than previously thought.

“We really have to rethink the risk from airbursts. Chelyabinsk was unusual due to the a low inclination at which it entered the atmosphere, but 90 percent of objects enter the atmosphere at a steeper angle and cause more damage on the surface,” Boslough said. That paper, which he wrote two years ago, was recently published online in Acta Astronautica.

The Chelyabinsk fireball is something those who saw it will never forget, and neither will Boslough.

“What’s amazing to me though, when you think about it, this is part of an asteroid that had been, floating through space, orbiting the sun for billions of years” he said for the documentary in a late February interview. “And two weeks ago, it exploded in the atmosphere, dropped to the ground, and here I am holding it in my hand! That’s amazing.”

View two airburst simulations or see photos at Sandia’s asteroid airburst Flickr set.

Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corp., for the U.S. Department of Energy’s National Nuclear Security Administration. With main facilities in Albuquerque, N.M., and Livermore, Calif., Sandia has major R&D responsibilities in national security, energy and environmental technologies and economic competitiveness.

Space policy roundup – Nov.26.13

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