NASA - NASA Ends Attempts to Fully Recover Kepler Spacecraft, Potential New Missions Considered

NASA Ends Attempts to Fully Recover Kepler Spacecraft, Potential New Missions Considered

Following months of analysis and testing, the Kepler Space Telescope team is ending its attempts to restore the spacecraft to full working order, and now is considering what new science research it can carry out in its current condition.

Two of Kepler's four gyroscope-like reaction wheels, which are used to precisely point the spacecraft, have failed. The first was lost in July 2012, and the second in May. Engineers' efforts to restore at least one of the wheels have been unsuccessful.

Kepler completed its prime mission in November 2012 and began its four-year extended mission at that time. However, the spacecraft needs three functioning wheels to continue its search for 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. As scientists analyze previously collected data, the Kepler team also is looking into whether the space telescope can conduct a different type of science program, including an exoplanet search, using the remaining two good reaction wheels and thrusters.

"Kepler has made extraordinary discoveries in finding exoplanets including several super-Earths in the habitable zone," said John Grunsfeld, associate administrator for NASA's Science Mission Directorate in Washington. "Knowing that Kepler has successfully collected all the data from its prime mission, I am confident that more amazing discoveries are on the horizon."

On Aug. 8, engineers conducted a system-level performance test to evaluate Kepler's current capabilities. They determined wheel 2, which failed last year, can no longer provide the precision pointing necessary for science data collection. The spacecraft was returned to its point rest state, which is a stable configuration where Kepler uses thrusters to control its pointing with minimal fuel use.

"At the beginning of our mission, no one knew if Earth-size planets were abundant in the galaxy. If they were rare, we might be alone," said William Borucki, Kepler science principal investigator at NASA's Ames Research Center in Moffett Field, Calif. "Now at the completion of Kepler observations, the data holds the answer to the question that inspired the mission: Are Earths in the habitable zone of stars like our sun common or rare?

An engineering study will be conducted on the modifications required to manage science operations with the spacecraft using a combination of its remaining two good reaction wheels and thrusters for spacecraft attitude control.

Informed by contributions from the broader science community in response to the call for scientific white papers announced Aug. 2, the Kepler project team will perform a study to identify possible science opportunities for a two-wheel Kepler mission.

Depending on the outcome of these studies, which are expected to be completed later this year, NASA will assess the scientific priority of a two-wheel Kepler mission. Such an assessment may include prioritization relative to other NASA astrophysics missions competing for operational funding at the NASA Senior Review board early next year.

From the data collected in the first half of its mission, Kepler has confirmed 135 exoplanets and identified over 3,500 candidates. The team continues to analyze all four years of collected data, expecting hundreds, if not thousands, of new discoveries including the long-awaited Earth-size planets in the habitable zone of sun-like stars. Though the spacecraft will no longer operate with its unparalleled precision pointing, scientists expect Kepler’s most interesting discoveries are still to come. 

Meanwhile, preparations are underway for hosting the second Kepler Science Conference Nov. 4-8, at NASA's Ames Research Center. This will be an opportunity to share not only the investigations of the Kepler project team, but also those of the wider science community using publicly accessible data from Kepler. Registration is now open. For more information about Kepler's upcoming science conference, visit:

http://go.nasa.gov/13kz012

For more information about NASA's call for two-wheel science proposals, visit:

http://go.nasa.gov/1a1UzaC

For more information about NASA's Kepler spacecraft, visit:

http://www.nasa.gov/kepler

NASA

Guillermo Gonzalo Sánchez Achutegui

ayabaca@gmail.com

ayabaca@hotmail.com

ayabaca@yahoo.com

NASA - New NASA Kepler Mission Data Q&A

New NASA Kepler Mission Data

05.31.2013

 

 

This diagram illustrates the flow of Kepler data through the stages of becoming a planet candidate.
Image credit: NASA Ames/W. Stenzel

On May 28, 2013, NASA's Kepler mission delivered new data to the NASA Exoplanet Archive. I sat down with Michael Haas, Kepler science office director at NASA Ames Research Center, to find out more.

MJ: Mike, what information has the Kepler mission recently delivered to the NASA Exoplanet Archive?
MH: The Kepler mission has just opened the Q1-Q12 activity table at the NASA Exoplanet Archive and delivered a majority of the Kepler Objects of Interest (KOIs) found by searching the data from Quarters 1 to 12 (May 2009 – March 2012) for transit-like signatures. In addition to finding many KOIs that were known from earlier searches of smaller data sets, the current delivery also includes 1,924 new KOIs.

MJ: That's exciting! Does this mean that the Kepler mission has added 1,924 new planet candidates to the count?
MH: No. The 1,924 new KOIs have not been completely analyzed yet. The term KOI means exactly what the name implies – Kepler has declared these to be “objects of interest,” not planetary candidates. By promoting these transit-like signatures to KOI status, all we are saying is that their light curves contain interesting patterns of repetitive dips that might indicate the presence of a transiting planet.

However, there are several other ways to produce similar looking transit-like patterns. For example, the dips could be due to stellar variability, excess detector noise, other transient events associated with the spacecraft, or a background star occulting a second background star (i.e., a background eclipsing binary). We use the term “false positive” to describe those KOIs that are explainable by means other than the planetary hypothesis. We know that with further analysis, many of these new KOIs will become false positives.

MJ: If you haven’t finished the analysis, why are you releasing this information now? It seems rather preliminary.
MH: You are right, it is preliminary, but it also represents a significant body of work and contains valuable information for the scientific community.

Remember how this process works. We started with the light curves of 192,313 stars that were observed for some or all of Quarters 1-12. That’s a lot of data to plow through. When we began searching the Q1-Q12 data last fall, we identified 18,406 threshold-crossing events (TCEs). These TCEs had to pass a series of tests, each with a threshold, that were designed to identify the events that look transit-like. This list of TCEs and their accompanying diagnostic reports (i.e., data validation reports and one-page summaries) were released to the public through the NASA Exoplanet Archive in December 2012.

The criteria required to pass this first set of tests are intentionally lenient. We prefer to include many non-transit-like events at this early stage of analysis, rather than to miss some really good events (i.e., small, Earth-size candidates in the habitable zone – the hardest candidates to find).

MJ: So, what happens next? Have you been analyzing the Q1-Q12 TCEs to figure out which are the most interesting?
MH: That is exactly right. We evaluated each TCE using objective criteria that are difficult to program into a computer. This exercise is called “triage” because it is a relatively quick assessment that eliminates the obvious false positives, while retaining anything that looks even remotely transit-like for further assessment. During this exercise, most of the events produced by spacecraft transients and stellar variability were discarded. This is process step 1 in the figure 'The Making of Kepler Planet Candidates.'

MJ: Is every TCE that passes triage automatically promoted to KOI status?
MH: No. If at least two scientists determine that a TCE looks transit-like, then the light curve is fit with a computer model of a transiting planet. If the model fit looks reasonable, then the TCE is promoted to KOI status. If the model fit is poor, then the TCE is ignored and receives no further analysis. As shown in the figure, slightly more than half of the TCEs that passed triage were promoted to KOI status.

Moreover, many of the KOIs found amongst the Q1-Q12 TCEs are old ones that were discovered and cataloged during previous transit searches – we have set these old KOIs aside for now. The remaining 1,924 KOIs are brand new. In the coming months, we will focus our attention on this set of new KOIs. We know that many of them will eventually become false positives, but we can now afford the additional analysis because we have reduced the number of light curves that require in-depth assessment by a factor of 100 (from 192,313 to 1,924).

MJ: Does that mean you don’t have to reanalyze the old KOIs?
MH: No, not at all. With more quarters of data and major improvements in our diagnostic tools, some of these old KOIs will change status when we disposition them again. (See process step 3 in the figure.) Some planet candidates will become false positives and some false positives will become planet candidates. It will be fun and extremely interesting to see how this all shakes out.

MJ: So, does this mean you will redisposition all the old KOIs as well as disposition the new KOIs?
MH: That is the long-term plan. However, it is not possible to complete all this work before the Q1-Q16 search results become available later this summer. Hence, we plan to disposition all of the new Q1-Q12 KOIs over the next few months, and then plan to redisposition the old KOIs using all 16 quarters of data and even better diagnostic tools that are currently under development.

MJ: With previous Kepler data releases, the term 'KOI' was synonymous with planet candidate. Can you explain what has changed?
MH: This is a common misperception. Actually, the definition of KOI has not changed; but our reporting philosophy has. In the past, the Kepler mission published lists of KOIs that were deemed to be planet candidates; and separately posted the KOIs that were declared false positives at MAST (Mikulski Archive for Space Telescopes). This may have given some the mistaken impression that all KOIs are planet candidates, but this has never been the case. For example, four of the first ten KOIs identified using the first month of data are currently marked as false positives in the cumulative activity table at the NASA Exoplanet Archive.

The reporting philosophy has been modified so that all KOIs can be archived in one place. This makes it much easier to change the status of a KOI from ‘planet candidate’ to ‘false positive,’ and vice versa. In addition, the new format enables more rapid release of incremental information as progress is made.

MJ: In the Q1-Q12 data set there are a surprising number of KOIs with orbital periods near one Earth-year. Do Earth-size planets tend to prefer Earth-like periods?
MH: Excellent question. Remember that the Kepler spacecraft orbits the sun every 371 days. Given its extremely stable environment, some noise sources associated with the local detector electronics exhibit repetitive behavior with this periodicity. Since these electronics read-out the charge-coupled devices (CCDs), this noise is intertwined with the astronomical signals in such a way that the two are almost impossible to disentangle. Hence, this repetitive noise can mimic the signature of a transiting planet.

Fortunately, we can identify these noise-produced TCEs and distinguish them from true planet candidates in one Earth-year orbits, but it requires a lot of effort. Although most of these bogus TCEs were ignored at the triage or model fitting stage, a small fraction of them have crept into the KOI population and still need to be identified and declared false positives. That work will occur over the next few months. Meanwhile, don’t get too hyped up by the pile-up of KOIs with one Earth-year periods, or the smaller, associated pile-up at 180 days. Most of these are probably not real planet candidates; then again, there may be some real gems there – that’s what makes this work so exciting.

This explanation is well documented in the Q1-Q12 TCE Release Notes [PDF] at the archive.

MJ: If that is the case, then why weren’t these bogus one Earth-year TCEs and KOIs seen in earlier releases?
MH: Remember that the Kepler spacecraft is in a 371-day orbit (i.e., just over one Earth-year) and that three transits are required to define a TCE (and therefore a KOI). Hence, we have just begun to see these bogus events now because we have searched three years (i.e., 12 quarters) of data for the first time.

MJ: Are there other reasons for an increased number of false positives in the Q1-Q12 delivery?
MH: Yes. In the past we have tossed out the eclipsing binaries (EBs) as soon as they were identified, so many of them have never been made into KOIs. This means that every time we search a dataset for transits, we end up finding and re-evaluating the EBs again. Once we realized this, we decided to retain all those found in the Q1-Q12 search, pass them through triage, fit models to them, and turn them into KOIs. Now they can be documented as false positives, giving us a lasting record of past decisions that help to minimize the amount of work going forward.

So yes, there are likely to be a higher percentage of EBs in this set of 1,924 KOIs than have been seen in past releases.

MJ: You mentioned earlier that this represents the “majority of the KOIs” found in Q1-Q12. Are you holding some back?
MH: We have finished triage and have identified KOIs up to 4914. That is the final KOI number for the Q1-Q12 search, but there are gaps (i.e., some KOIs are missing) in this first delivery because they are troublesome cases that require manual processing. For example, some KOIs were found in the initial computer search of the Q1-Q12 data, but their properties were incorrectly calculated. For these KOIs, we need to recompute their properties before they can be delivered.

By staging the deliveries as we have done, the best information is delivered to the community in a timely fashion rather than waiting for a complete analysis of all KOIs.

MJ: To summarize, the new 1,924 KOIs are not fully analyzed and not all the Q1-Q12 KOIs have been delivered yet. What guidance do you have for the scientific community about using the Q1-Q12 data now?
MH: The value of this delivery greatly depends on your scientific objectives. If you are looking for interesting KOIs to study or observe, then we have narrowed the search down from 192,313 light curves to 1,924. That’s a big help. If you are trying to understand the statistical population of small planets in the galaxy, this delivery isn’t going to hand you what you need right now. Stay tuned; good planets are hard to find. A team member once said that searching for planets is not like “looking for a needle in a haystack,” but more like looking for an aluminum needle made out of one aluminum alloy in a pile of needles made out of a different alloy. This delivery is an important step in that type of process.

The NASA Exoplanet Archive is funded by NASA's Exoplanet Exploration Program to collect and make data public to support the search for and characterization of exoplanets and their host stars. The archive is hosted at the Infrared Processing and Analysis Center at the California Institute of Technology.

For information about the NASA Exoplanet Archive, click here.

For information about the Kepler Mission, click here.
Michele Johnson

Ames Research Center, Moffett Field, Calif.

NASA

Guillermo Gonzalo Sánchez Achutegui

ayabaca@gmail.com

ayabaca@hotmail.com

ayabaca@yahoo.com

Astronomy: Compact Planetary System

Hi My Friends: AL VUELO DE UN QUINDE EL BLOG., This artist's concept depicts a planetary system so compact that it's more like Jupiter and its moons than a star and its planets. Astronomers using data from NASA's Kepler mission and ground-based telescopes recently confirmed that the system, called KOI-961, hosts the three smallest exoplanets currently known to orbit a star other than our sun. An exoplanet is a planet that resides outside of our solar system.Compact Planetary System
This artist's concept depicts a planetary system so compact that it's more like Jupiter and its moons than a star and its planets. Astronomers using data from NASA's Kepler mission and ground-based telescopes recently confirmed that the system, called KOI-961, hosts the three smallest exoplanets currently known to orbit a star other than our sun. An exoplanet is a planet that resides outside of our solar system.

The star, which is located about 130 light-years away in the Cygnus constellation, is a red dwarf that is one-sixth the size of the sun, or just 70 percent bigger than Jupiter. The star is also cooler than our sun, and gives off more red light than yellow.

The smallest of the three planets, called KOI-961.03, is actually located the farthest from the star, and is pictured in the foreground. This planet is about the size of Mars, with a radius of 0.57 times that of Earth. The next planet to the upper right is KOI-961.01, which is 0.78 times the radius of Earth. The planet closest to the star is KOI-961.02, with a radius 0.73 times the Earth's.

All three planets whip around the star in less than two days, with the closest planet taking less than half a day. Their close proximity to the star also means they are scorching hot, with temperatures ranging from 350 to 836 degrees Fahrenheit (176 to 447 degrees Celsius). The star's habitable zone, or the region where liquid water could exist, is located far beyond the planets.

The ground-based observations contributing to these discoveries were made with the Palomar Observatory, near San Diego, Calif., and the W.M. Keck Observatory atop Mauna Kea in Hawaii.

Image Credit: NASA/JPL-Caltech
NASA.

Guillermo Gonzalo Sánchez Achutegui

ayabaca@gmail.com

ayabaca@hotmail.com

ayabaca@yahoo.com

Astronomy: NASA's Kepler Releases New Catalog- 2,321 Planet Candidates

Hi My Friends: AL VUELO DE UN QUINDE EL BLOG., The histogram summarizes the findings in the Feb. 27, 2012 Kepler Planet Candidate catalog release. The catalog contains 2,321 planet candidates identified during the first 16 months of observation conducted May 2009 to September 2010. Of the 46 planet candidates found in the habitable zone, the region in the planetary system where liquid water could exist, ten of these candidates are near-Earth-size. Kepler Planet Candidates by Size, Feb. 27, 2012
The histogram summarizes the findings in the Feb. 27, 2012 Kepler Planet Candidate catalog release. The catalog contains 2,321 planet candidates identified during the first 16 months of observation conducted May 2009 to September 2010. Of the 46 planet candidates found in the habitable zone, the region in the planetary system where liquid water could exist, ten of these candidates are near-Earth-size.

Credit: NASA Ames/Wendy Stenzel.

Since science operations began in May 2009, the Kepler team has released two catalogs of transiting planet candidates. The first catalog (Borucki et al, 2010), released in June 2010, contains 312 candidates identified in the first 43 days of Kepler data. The second catalog (Borucki et al, 2011), released in February 2011, is a cumulative catalog containing 1,235 candidates identified in the first 13 months of data.

Today the team presents the third catalog containing 1,091 new planet candidates identified in the first 16 months of observation conducted May 2009 to September 2010. These are the same candidates that the team discussed at the Kepler Science Conference held at NASA Ames Research Center in December 2011.

Here are the highlights of the new catalog:
A.- Planet candidates smaller than twice the size of Earth increased by 197 percent, compared to 52 percent for candidates larger than twice the size of Earth.
B.- Planet candidates with orbital periods longer than 50 days increased by 123 percent, compared to 85 percent for candidates with orbital periods shorter than 50 days. Since the last catalog was released in February 2011, the number of planet candidates identified by Kepler has increased by 88 percent and now totals 2,321 transiting 1,790 stars.

The cumulative catalog now contains well over 200 Earth-size planet candidates and more than 900 that are smaller than twice Earth-size. Of the 46 planet candidates found in the habitable zone, the region in the planetary system where liquid water could exist, ten of these candidates are near-Earth-size.

The number of planetary systems found with more than one planet candidate also has increased. Last year, 17 percent, or 170 stars, had more than one transiting planet candidate. Today, 20 percent, or 365, stars have more than one.

"With each new catalog release a clear progression toward smaller planets at longer orbital periods is emerging, " said Natalie Batalha, Kepler deputy science team lead at San Jose State University in California. "This suggests that Earth-size planets in the habitable zone are forthcoming if, indeed, such planets are abundant.

"Nearly 5,000 periodic transit-like signals were analyzed with known spacecraft instrumentation and astrophysical phenomena that could masquerade as transits, which can produce false positives. The most common false positive signatures are associated with eclipsing binary stars- a pair of orbiting stars that eclipse each other from the vantage point of the spacecraft.

The Kepler space telescope identifies planet candidates by repeatedly measuring the change in brightness of more than 150,000 stars in search of planets that pass in front, or "transit," their host star. Kepler must record at least three transits to verify a signal as a planet.

The findings are published in the "Planetary Candidates Observed by Kepler III: Analysis of the First 16 Months of Data".

The catalog is available at the Kepler data archive at the Space Telescope Science Institute and can be downloaded from the NASA Exoplanet Archive.

NASA's Ames Research Center in Moffett Field, Calif., manages Kepler's ground system development, mission operations and science data analysis. NASA’s Jet Propulsion Laboratory, Pasadena, Calif., managed the Kepler mission's development.

Ball Aerospace and Technologies Corp. in Boulder, Colo., developed the Kepler flight system and supports mission operations with the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder.

The Space Telescope Science Institute in Baltimore archives, hosts and distributes Kepler science data. Kepler is NASA's 10th Discovery Mission and is funded by NASA's Science Mission Directorate at the agency's headquarters in Washington.

For information about the Kepler Mission,

visit: http://www.nasa.gov/kepler
Guillermo Gonzalo Sánchez Achutegui
ayabaca@gmail.com

ayabaca@hotmail.com

ayabaca@yahoo.com