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Kepler Guest Observer Program

Guest Observer (GO) Program

Kepler's high-precision photometry, with short cadence and long cadence modes (1 minute and 30-minute exposures), provides a powerful tool for variability analyses of both Galactic and extragalactic sources. Pointed observations away from the single stare position of the mission cannot be accommodated by Kepler; all targets, including GO targets, are limited to the objects available in the fixed FOV. Application to the Kepler GO program is open to all investigators, including those from outside the U.S. under NASA’s no-exchange-of-funds policy. Investigators who are not affiliated with a U.S. institution are not eligible for funding through this program. GO cycles occur annually and begin in June of each year. The data will be placed into the public archive at MAST. From Oct 2012, there is no exclusive use period for any Kepler data, including data collected through the GO program. GO funding will start upon availability of data to the PI within the archive.

One of three reaction wheels required for Kepler to maintain fine-point observations failed on May 14, 2013. New Kepler observations through the Guest Observer program remain on hold while future spacecraft operation scenarious using three reaction wheels, or an assisted two-wheel mode, are explored. The reaction wheel failed during the final quarter (Q17) of Guest Observer cycle 4. Cycle 5 programs had been selected before the failure occurred. Selected cycle 5 programs are currently kept on hold while the quality of future Kepler observations under new observing modes (if any are proved viable) are determined.


The GO program is inclusive of both exoplanet programs and non-exoplanet programs. The Kepler GO program is open to:

  1. proposals addressing any area of planetary, stellar or extragalactic astrophysics that does not repeat the primary goals (1.1-1.3) of the Kepler extended mission.
  2. proposals for short cadence observations of known exoplanet candidates that are not currently being observed in short cadence.
  3. proposals for long cadence observations of new targets for the identification of planets transits.

Proposers should note that short cadence resources are in high demand and heavily over-subscribed. Short cadence proposals must justify scientifically and technically the need for higher cadence monitoring in the context of existing or on-going long cadence observations.

Proposers must take account of the difference between science that can be achieved exclusively using archived data and science that requires new observations by Kepler. The GO program is specific to science requiring new observations. This can mean completely new targets, or the collection of more data from old or existing targets. Funding for purely archival science is provided through the ROSES 2013 ADAP program. All proposals must justify the need for new observational data within their program.

No current Kepler targets are guaranteed to be observed during a GO cycle, except the list of existing exoplanet candidates. All other survey targets could potentially be dropped from the observational list for scientific or operational reasons. By successfully proposing an existing target through the GO program, the proposer guarantees the observation of that target during the next GO cycle, regardless of whether the target is removed from the exoplanet survey list.

All science proposals must be compelling and carefully justified scientifically and technically. Proposals with novel scientific objectives or approaches that expand the current range of science issues to be addressed using Kepler data, capitalize on the mission’s unique capabilities, and minimize replication of ongoing investigations, are encouraged.


Proposals cycles are annual. Proposals are due each Jan. Observations for successful programs begin in Jun and end in Jun the following year. GO cycles are divided into four operational quarters, separated by the quarterly rolls of the spacecraft. Proposer provide targets to be observed over the cycle. A new target list is uploaded to the spacecraft before every quarter. Long cadence GO targets can be removed or added to the target list every quarter. Short cadence GO targets can be removed or added to the target list every month. Data from a specific GO cycle arrive at the MAST archive for the first time in Jan of the following year.


Itemized instructions for developing and submitting a GO proposal can be found here.


The standard GO competition occurs on an annual cycle. Given the proposal review timeline, associated data processing and archive activities, there is currently a 6-month delay between GO proposal submission and first observations, and a 1-year wait between proposal submission and the delivery of the first GO data. To provide a faster mechanism for headline Kepler astrophysics, we provide an alternative means for acquiring Kepler data, through the Director's Discretionary Target (DDT) program.

The purpose of the DDT program is to:

  • Provide a fast-track to Kepler data, yielding rapid, high-impact science.
  • Respond to targets of GO interest, newly dropped from the planetary list. Targets can be reinstated back into the observing list via a DDT request.
  • Respond to "targets of opportunity".
  • Permit pilot studies of small samples prior to the next GO solicitation.

The DDT program is a quarterly competition. Observations can be proposed for at any time; approved targets will be added during the next spacecraft roll. Up to 100 DDTs are available each quarter. No funding will be provided for DDTs. Proposals from all institutions and countries are encouraged. The proposal process requires a one page scientific justification and target list delivered to the . DDT proposals can be submitted at any time, however in order to include sources within the next available quarter proposers must submit requests before these dates: Jan 24, Apr 23, Jul 24, Oct 24. Target overlap with the current Guest Observer observing list will not be considered unless short cadence observations are being requested of a current long cadence target. In the event that DDT requests are oversubscribed, DDT proposals will be reviewed and prioritized by the Kepler Users' Panel (KUP).

Questions concerning Kepler's science opportunities and open programs, public archive or community tools? Contact us via the email address.
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Editor: Martin Still
NASA Official: Jessie Dotson
Last Updated: Jan 11, 2013
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