Kepler Two-Wheel White Papers

by Dr. Tahir Yaqoob on October 13, 2013

Many apologies for the long gap in articles, due to a change in my job situation.On the exoplanet front there have been some important developments with the Kepler mission. But first of all, it’s worth mentioning that at the time of writing, the number of confirmed planets outside of our solar system is just shy of 1000. There are 998 confirmed planets, residing in 759 planetary systems, of which 169 are multiplanet systems, according to the Extrasolar Planet Encyclopedia. More details about the demographics will follow in a future article.

At the time of writing all the NASA websites are down because of the government shutdown, so I won’t include any hyperlinks here. Earlier in the year, the Kepler spacecraft lost the use of two of four gyroscopic wheels that enable precision pointing on which the exoplanet science that it was designed for relies upon. The end result is that although data can still be collected, the precision of the pointing is severely compromised to the extent that the original science investigations cannot be continued. Recall that the Kepler mission studied a fixed region of the sky, searching for exoplanets around stars in that region, and characterizing some of the physical properties of the exoplanet candidates that were found. NASA then released a solicitation for proposals to use the degraded capability with a view to selecting one proposal for a program that would make the best scientific use of the crippled spacecraft and its instruments.

The solicitation resulted in a total of 42 proposals and I thought it would be useful in this article to summarize those proposals in an accessible way. What is interesting is that all of the proposals can be placed in just four simple categories. These are:

(1) Physics and Evolution of Stars [12 proposals]
In this category the proposals basically say, forget about planets, let’s use Kepler to study stars, for which the high-precision pointing capability is not essential. There are some important unsolved problems in stellar physics and the proposals cover a variety of topics related to the physics and evolution of stars.Some proposals advocate studying clusters of stars for evolutionary properties, others suggest studying stellar seismology (pulsations) to probe the internal structure of stars, and yet other propose to study stars with high-amplitude variability.

(2) Continue Exoplanet Studies Despite the Limited Control [18 proposals]

Formally, this category had the most number of proposals (which might sort of be expected), but the number is only marginally larger than the stellar physics and evolution category. There are some very creative and interesting ideas in these proposals with suggestions of how to continue to study exoplanets. How each proposed idea tackles the technical issues associated with the degradation of pointing accuracy varies a lot from proposal to proposal, as does the depth of feasibility study. Some of the proposals advocate using cleverer ways to analyze the data in order to recover some of the loss in pointing precision (i.e. they amount to improvements in the analysis software).

In order to mitigate the problems, various strategies are proposed in different proposals. Some suggest targeting certain classes of exoplanet with particular mass and size ranges, or targeting certain types of stars, whilst others suggest pointing at particular regions of the sky since the pointing accuracy is not the same for every direction.

As an example, one proposal (Habitable Planets Around White Dwarfs:
an Alternate Mission for the Kepler Spacecraft
, by M. Kilic et a.) suggests targeting so-called White Dwarf (WD) stars. These are stars that are at an advanced stage in their evolution, having exhausted their hydrogen and helium supplies, to become very compact objects. WD stars are as common as sun-like stars and can potentially provide the energy source for planets for billions of years. It is argued that transiting planets in the habitable zone may be common around WD stars. The proposal suggests a survey of WDs lasting 200 days, from which the authors claim they will find about 100 planets in the habitable zone. The authors argue that for the proposed science the limiting precision factor is not the accuracy of the pointing but the brightness of the targeted WD. Since WDs are physically smaller in size than the a sun-like star of the same brightness, the eclipse signature against a WD has a higher “contrast” for a given planet size.

(3) Studies of Things that are Not Exoplanets or Stars [11 proposals]

This category also has a sizeable number of proposals, nearly the same number as for the (1), the study of stars. There is an interesting variety of astrophysical objects targeted in this category. Some target galaxies known as “active galaxies,” which are closely related to quasars. Others target asteroids and/or near-Earth object studies (In fact, 4 of the 11 proposals are in this subcategory). One proposal advocates the study of a particular comet. Interestingly, one proposal targets a planet in our solar system – Neptune. The proposed science aims at studying the interior structure of the ice giant by means of analyzing its oscillation modes. The proposal highlights a feature that is commonly pointed in many of the proposals in this and other categories, that is that the pointing precision of Kepler with only two wheels has the best precision when the field of view is in the spacecrafts orbital plane (the ecliptic plane) which of course also includes the plane that most of the solar system planets lie close to. There are a couple of proposals in category (3) that have very general aims, with an appropriately general title. For example, Kepler Alternative Science: Many Possibilities is the simple and straightforward title of a proposal by P. R. McCullough and a team at the Hubble Space Telescope Science Institute (STScI).

(4) Use Kepler to Obtain Calibration Data to Get More Out of Existing Data [1 proposals]

This category has the smallest number of proposals and stands out as being different to the other three categories because the advocated use of Kepler is conceptually different. No new astrophysical targets are proposed, but instead it is advocated that we can now use Kepler to do calibration studies that will enable more and/or better science to be extracted from existing Kepler exoplanet data. The proposal advocates observing the same Kepler field as before but this time to make a systematic mapping of the region in order obtain better characterization of the instrument so-called “point-spread-function” which describes in detail how a point source of light is spread out by the telescope and instrumentation.

It will be interesting to see which program is selected, there are a lot of interesting propositions so the choice will be difficult. For convenience for those who want to read or browse the original papers, the titles of the 42 white papers are listed below, since all the NASA websites. A simple search in Google or other search engine will find the paper.

category: Physics and Evolution of Stars

MONITORING YOUNG ASSOCIATIONS AND OPEN CLUSTERS WITH KEPLER IN TWO-WHEEL MODE
[S. Aigrain, U. of Oxford]

ENSEMBLE ASTEROSEISMOLOGY OF THE YOUNG OPEN CLUSTER NGC 2244 (EASILY)
[Conny Aerts, U. of Leuven]

ASTEROSEISMOLOGY OF SOLAR-LIKE OSCILLATORS IN A 2-WHEEL MISSION
[W. J. Chaplin, U. of Birmingham]

A GYROCHRONOLOGY AND MICROVARIABILITY SURVEY OF THE MILKY WAY’S OLDER STARS USING KEPLER’S TWO-WHEELS PROGRAM
[Saurav Dhital, Embry-Riddle Aeronautical University]

THE SUN IN TIME: FROM THE YOUNG SUN TO THE CURRENT EPOCH
[Mark Giampapa, NOAO]

KEPLER RECONNAISSANCE OF ULTRACOOL DWARFS
[John E. Gizis, U. of Delaware]

OBSERVING OPEN CLUSTERS WITH A SEQUENCE OF AGES WITH KEPLER
[Joyce A. Guzik]

USING KEPLER TO PROBE LONG-PERIOD VARIABLES AND GALACTIC EVOLUTION
[K. E. Kraemer, Boston College]

THE KEP-CONT MISSION: CONTINUING THE OBSERVATION OF HIGH-AMPLITUDE VARIABLE STARS IN THE KEPLER FIELD OF VIEW
[L. Molnar]

THE KEPLER-SEP MISSION: HARVESTING THE SOUTH ECLIPTIC POLE LARGE-AMPLITUDE VARIABLES WITH KEPLER
[R. Szabo, Konkoly Observatory]

KEPLER’S UNPARALLELED EXPLORATION OF THE TIME DIMENSION (study binaries)
[William Welsh, San Diego State U.]

KeSeF – KEPLER SELF FOLLOW-UP MISSION
[Aviv Ofir, Georg-August-Universitat]

NEW USES FOR THE KEPLER TELESCOPE: A SURVEY OF THE ECLIPTIC PLANE FOR TRANSITING PLANETS AND STAR FORMATION
[C. Beichman, NExSci]

KEPLER 2.0: A SEARCH FOR SMALL PLANETS AROUND SMALL STARS
[Douglas Caldwell, SETI Institute]

TIME-OPTIMAL CONTROL IN SU(2) AND SO(3)
[Yuly Billig, Carleton U.]

PROPOSAL TO DETERMINE THE FREQUENCY OF LONG-PERIOD PLANETS IN THE HABITABLE ZONE OF SOLAR-LIKE STARS
[W. J. Boruki, NASA Ames Research Center]

SPACEDESIGN “KEPLER MAX BLUE” RESPONSE
[Joseph M. Clay, Spacedesign Corporation]

SEARCHING FOR TERRESTRIAL PLANETS ORBITING IN THE HABITABLE ZONE OF ULTRA-COOL STARS AND BROWN DWARFS
[Brice-Oliver Demory, MIT]

A HABITABLE ZONE CENSUS VIA TRANSIT TIMING AND THE IMPERATIVE FOR CONTINUING TO OBSERVE THE KEPLER FIELD
[Daniel C. Fabrycky, U. of Chicago]

MICROLENS PLANETS AND PARALLAXES
[Andrew Gould, Ohio State U.]

HABITABLE PLANETS AROUND WHITE DWARFS: AN ALTERNATE MISSION FOR THE KEPLER SPACECRAFT
[Mukremin Kilic, University of Oklahoma]

LOOKING FOR VERY SHORT-PERIOD PLANETS WITH A RE-PURPOSED KEPLER MISSION
[Brian Jackson, Carnegie Institution for Science]

KEPLER’S “SWEET SPOT”
[Charles F. Lillie]

TARGETING YOUNG STARS WITH KEPLER: PLANET FORMATION, MIGRATION MECHANISMS AND THE EARLY HISTORY OF PLANETARY SYSTEMS
[James P. Lloyd, Cornell University]

TRANSITS OF LILLIPUTIAN WORLDS AROUND NEARBY TINY STARS WITH KEPLER
[Eduardo L. Martin, U. of Florida]

HOT BIG PLANETS SURVEY: MEASURING THE REPOPULATION RATE OF THE SHORTEST-PERIOD PLANETS
[Stuart F. Taylor]

A RESPONSE FOR “CALL FOR WHITE PAPERS: SOLICITING COMMUNITY INPUT FOR ALTERNATE SCIENCE INVESTIGATIONS FOR THE KEPLER SPACECRAFT” FROM NASA
[Mohamed Salah Elghamry]

MAXIMIZING KEPLER SCIENCE RETURN PER TELEMETERED PIXEL: DETAILED MODELS OF THE FOCAL PLANE IN THE TWO-WHEEL ERA
[David Hogg, NYU.]

MAXIMIZING KEPLER SCIENCE RETURN PER TELEMETERED PIXEL: SEARCHING THE HABITABLE ZONES OF THE BRIGHTEST
[Benjamin T. Montet, CalTech]

SUB-PIXEL CALIBRATION TO ENABLE NEW SCIENCE INVESTIGATIONS UNDER KEPLER 2-WHEEL OPERATIONS
[Michael Shao, JPL]

category: Studies of Things that are Not Exoplanets or Stars

A PROPOSED 2-WHEEL OPERATION SCENARIO AND ALTERNATIVE SCIENCE INVESTIGATIONS FOR THE KEPLER SPACECRAFT
[Michael Carini, Western University of Kentucky]

SIMULTANEOUS ROSETTA IN SITU AND KEPLER REMOTE OBSERVATIONS OF THE TAIL AND COMA OF COMET 67P/CHURYUMOV-GERASIMENKO – Comets
[Niklas J. T. Edberg, Swedish Institute of Space Physics]

AGN VARIABILITY STUDIES WITH THE REPURPOSED KEPLER MISSION -AGN
[R. Edelson]

PRECISION ROTATION PERIODS AND SHAPES OF NEAR-EARTH ASTEROIDS
[Martin Elvis, SAO]

USING THE KEPLER SPACECRAFT TO SCAN THE NEARBY SOLAR SYSTEM FOR NEAR EARTH ORBIT OBJECTS
[Mark A. Huebner]

PROBING NEPTUNE WITH KEPLER
[Mark Marley, NASA Ames Research Center]

KEPLER ALTERNATIVE SCIENCE: MANY POSSIBILITIES
[P. R. McCullough, STScI]

WHITE PAPER FOR AN ALTERNATE SCIENCE INVESTIGATION FOR THE KEPLER SPACECRAFT
[Ames Research Center, Code DL] (protecting spacecraft)

NEOKepler: DISCOVERING NEAR-EARTH OBJECTS USING THE KEPLER SPACECRAFT
[Kevin B. Stevenson, U. of Chicago]

EXTRAGALACTIC SCIENCE WITH KEPLER IN TWO GYRO MODE, A WHITE PAPER
[Rob Olling, UMD]

REPURPOSING THE KEPLER SPACECRAFT TO SEARCH FOR NEAR EARTH OBJECTS
[David E. Trilling, Northern Arizona U.]

category: Use Kepler to Obtain Calibration Data to Get More Out of Existing Data

EXPANDING THE KEPLER LEGACY: DRIFT SCAN OBSERVATIONS TO SIGNIFICANTLY IMPROVE KEPLER ASTROMETRY
[Angelle Tanner, Mississippi State U.]

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