Overview

Depending upon the size of their target list and their own patience to detail, proposers may want to complete some or all of these checks to ensure that the proposed targets are both technically feasible and the program and photometry are optimized:

1. IS THE TARGET LISTED IN THE KEPLER INPUT CATALOG?
2. DOES THE TARGET FALL ON DETECTOR SILICON?
3. DOES THE TARGET FALL UPON THE DEAD CCD MODULE?
4. HAS THE TARGET BEEN OBSERVED BEFORE?
5. IS THE KEPLER INPUT CATALOG MAGNITUDE CORRECT?
6. DOES THE TARGET RESIDE IN A CROWDED FIELD?
7. IS THE TARGET AN EXTENDED SOURCE?
8. IS THE TARGET NEAR A BLEEDING COLUMN?
9. DOES THE TARGET HAVE A HIGH PROPER MOTION?

Is the target listed in the Kepler Input Catalog?

The Kepler Input Catalog (KIC) is the source of the physical target parameters provided by the Target Search Form. The catalog is largely complete to about Kp = 17 (Kp corresponds closely to the R-band for all but very red or blue sources). Most users will find their proposed targets in the KIC, uniquely labeled by Kepler ID number. In these cases, Kepler observations are generally routine. Pre-observation target management procedures performed by Kepler engineers utilize the KIC parameters to define pixel masks around each targets. Special handling by the proposer is required for sources proposed that are not listed in the KIC. The proposer must supply a custom-defined pixel mask for the target. The custom mask can be supplied using the software described here. The GO Office will only request custom masks from proposers after their proposal is accepted.

Does the target fall upon detector silicon?

The simple answer is "yes" if the target is returned by the Target Search Form. Targets falling within the chip gaps and outside of the field of view are not returned by the form.

If a bone fide target is not listed in the KIC, users can determine whether specific celestial coordinates fall upon silicon using our Google Sky facility or the Kepler Full Frame Images.

Sources within a few pixels of a CCD edge will be dropped from the target list when the assigned photometric aperture abuts or extends beyond the edge. Use the Target Search Form to download the four Edge_Distance parameters, one for each season (rotation orientation of the spacecraft). If you can, avoid sources within an edge distance of a few pixels. Due to aberration over the quarter, these targets are at risk.

Does the target fall upon the dead CCD module?

CCD module 3, comprising detector channels 5, 6, 7, and 8 failed during Quarter 4. Any source which falls on module 3 during a specific quarter cannot be observed during that quarter. The spacecraft rotates four times a year, therefore the module falls on four different regions of sky each year. Long-term photometry of such targets will have a 3-month long gap. The Target Search Fool identifies sources falling on module 3. Note that the default search form does not yield the required information. The user must add the four "Module_#" parameters to the listing using the dialog box located below the "Output Columns" list. Alternatively click the "add all" button.

Figure 1: Google Sky snapshot of the Kepler field of view and detector array. The identity of individual mod.outs (channels) is marked by scrolling the mouse. Here, mod.out 3.3 (channel 7) is indicated, conveying the location of the dead module.

Has the target been observed before?

The GO Target Allocation Committee will take existing archived data into consideration when assessing the scientific potential of proposed observations. Users can determine the observational history of a source from the Target Search Form. The target attribute called "Availability Flag" has three conditions:

• 0   –   No data has been taken
• 1   –   This target is being observed but data has not yet been ingested in the archive
• 2   –   Data exists in the archive for this target

Proposers can examine the KASC (asteroseismology) target list, published on their webpage.

Lists of Guest Observer targets are obtained from the links in the table below, one text file per quarter. Each file lists the Kepler ID, the associated GO program and the observing cadence.

Is the Kepler Input Catalog magnitude correct?

Magnitude and celestial position are the fundamental attributes of a target for defining the size of the pixel mask. If (a) a target is listed in the KIC but has no Kepler magnitude, or (b) the target is not listed in the KIC, or (c) the KIC magnitude is incorrect due to e.g. temporal variability, the recommended steps are:

1. Estimate Kp using e.g. the instructions and formula on the Kepler Calibration page.
2. Enter the estimate on the Target Table, and note that the value is a user-supplied estimate.
3. Briefly describe the method used to arrive at your estimated Kp in the section of your proposal describing source selection.

Does the target reside in a crowded field?

Kepler target apertures contain light from the target, background and foreground sources. Contaminants within the aperture result in systematic artifacts which can be mitigated for with varying degrees of success during data reduction. However artifacts can also be reduced before data is collected by choosing target samples that minimize stellar contamination. The "Crowding_season" attribute provided by the Target Search Form predicts the fraction of light due to neighboring sources within a target aperture. The Crowding_season attribute can therefore be employed to purify target samples.

Is the target an extended source?

The Kepler field and the KIC contain identified and unidentified galaxies. Galaxies provide Kepler target management with two challenges.

1. Location: Structures in the galaxy such as HII regions are often listed as separate KIC entries. The Kepler Input Catalog therefore often contains multiple entries for galaxies and the entry closest in position to your input coordinates may not be the most appropriate ID. An example is provided in figure 3.

2. Extent: In general, galaxies are extended objects whereas Kepler's pixel apertures assume all targets are point sources.

Figure 3: DSS image of the galaxy UGC 11446 (KIC 6044188 with Kp = 9.7). The FOV is 2.5 arcmin on a side. There are 20 KIC sources (red crosses) within 30 arcsec of the galaxy center. Some of these sources are not real.

The GO Office will mitigate for extended targets by adding extra pixel halos around the apertures. By default, a halo of width 1 pixel will be added to standard masks around extended targets Kp < 11. A two-pixel wide halo will be added to standard masks around extended targets 11 < Kp < 16. A halo of width 3 pixels will be added to standard masks around extended targets Kp > 16. Mitigation steps for the proposer are:

• The user should perform a cone search around the galaxy coordinates listed at e.g. NASA's Extragalactic Database (NED) using a search radius matching the galaxy's angular diameter. Adopt the KIC source located within the footprint of the galaxy that is the brightest in Kp magnitude.

• Indicate in the comment column on the proposal target table that the target is extended and you request a pixel halo.

• If the KIC value appears to be in serious disagreement with an estimate based upon independent photometry, Indicate this in the comment column of the proposal target table.

• If a successful proposer for extended target science requires pixel masks of a different size than those provided by the default halos, they must submit custom mask files defining the full list and location of pixels required - one file for each target in their program. Each file needs to be re-delivered before each operational quarter in order to define new pixels after each spacecraft role. Deadlines for delivery of custom mask files every year are:

  Apr 23	Q(4a - 2)
  Jul 24	Q(4a - 1)
  Oct 24	Q(4a)
  Jan 24	Q(4a + 1)

  a is the GO cycle number.

Is the target near a bleeding column?

There are 734 stars in the Kepler field with Kp < 9.0. The level of CCD saturation in these sources bleeds charge into neighboring pixels. Bleeding compromises photometry of nearby stars whose apertures lie in the bleeding columns. The number of problematic stars is small. Check for nearby bright stars in the vicinity of your target using the Target Search Form.

Figure 4: A Quarter 1 FFI local to the Kp = 5.8 star KIC 5385723 (HD 187879). Charge bleed extends over 220 pixels rows and numerous neighboring stars. Science from stars contaminated by charge bleeds from nearby targets is often impossible. Conversely, target saturation does not pose a problem to photometry of the saturated star provided a large pixel mask fully-captures the bleeding charge.

Does the target have a high proper motion?

If you choose to provide proper-motion corrected coordinates, please indicate this change on the Target Table form. The GO Office will work with successful proposers to ensure accurate placement of target apertures over high proper motion stars.