GPIPS

GPIPS Status

GPIPS is a current, ongoing project to study magnetic fields via the polarization of infrared light from the Galactic plane. More information about the project's goals can be found on the About > Key_Science page of this website. GPIPS has completed eight observing seasons and and all fields have been observed. This web page is intended to keep interested parties up-to-date on the survey progress. (now complete)

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Observations Status
Data Processing Status
Data Release Plan
Data Collection Methodology

Observations Status

2015.12.04 - About 50 fields were found to have poor quality data and were reobserved in 201505 and 201510. Since then, detailed examination of the GPIPS data products and application of a new quality control criterion ('secular amplitude' limited to < 2.5%) flagged another 36 fields for rejection. At present, those 36 fields are planned for reobservation in May-June 2016, as are another 139 fields having less serious, but non-ideal, problems and issues. All GPIPS data will be released as DR4 in/around July-Aug 2016.

2014.03.06 - All GPIPS data have been calibrated in final form (PPOL v8.2.1) and are undergoing final staging in preparation for full release of the combined images and catalogs.

2013.11.15 - All GPIPS fields have been observed, and failed fields have been reobserved. All fields have passed quality control checks and have been processed through PPOL Step 8 and are awaiting final polarimetric calibration prior to release.

2013.07.10 - 99.69% of the fields have been observed successfully, to the 2 arcsec seeing criterion. The remaining 10 fields are expected to be completed later this month.

2012.10.15 - All 3,237 GPIPS fields have been examined at least once. Note, though, that on average about 5% of the fields still require a revisit to correct observing problems (chiefly poor seeing, but also autoguider probe incursion into the image zone, poor pointing, and wind shake).

Data Processing Status

GPIPS Data Processing Summary Table
Obs. Run
Start Date
End Date
Fields Obs.
BDP Date
BDP Ver
PPOL Date
PPOL Ver
Notes/Comp/Step
200606
20060610
20060706
152
2/24/2010
2.1.5
3/6/14

8.2.1

done
200609
20060904
20060914
9
2/23/2010
2.1.5
3/6/14
8.2.1
done
200706
20070525
20070704
335
2/22/2010
2.1.5
3/6/14
8.2.1
done
200709
20070918
20071008
186

2/16/2010

2.1.5
3/6/14
8.2.1
done
200805
20080521
20080530
52
2/16/2010
2.1.5
3/6/14
8.2.1
done
200806
20080607
20080701
343
2/14/2010
2.1.5
3/6/14
8.2.1
done
200809
20080909
20080924
113
2/9/2010
2.1.5
3/6/14
8.2.1
done
200903
20090308
20090308
2

3/1/2010

2.1.5
3/6/14
8.2.1
done
200905
20090509
20090515
66
2/16/2010
2.1.5
3/6/14
8.2.1
done
200906
20090603
20090710
260

2/9/2010

2.1.5
3/6/14
8.2.1
done
200909
20090929
20091010
89
2/9/2010
2.1.5
3/6/14
8.2.1
done
201005
20100523
2010605
217
7/30/2010
3.0.3
3/6/14
8.2.1
done
201006
20100618
20100630
275
7/17/2010
3.0.2
3/6/14
8.2.1
done
201009
20100918
20101001
235
12/23/2010
3.1.1
3/6/14
8.2.1
done
201105
20110514
20110521
42
6/2/2011
3.1.2
3/6/14
8.2.1
done
201106
20110609
20110625
395
8/5/2011
3.1.3
3/6/14
8.2.1
done
201109
20110910
20110919
43
11/1/2011
3.2.0
3/6/14
8.2.1
done
201110
20111008
20111020
182

11/28/11

3.2.1
3/6/14
8.2.1
done
201205
20120506
20120511
48

7/25/2012

3.2.3
3/6/14
8.2.1
done
201206
20120528
20120614
377
8/12/2012
3.2.3
3/6/14

8.2.1

done
201207
20120623
20120709
158
8/21/2012
3.2.3
3/6/14
8.2.1
done
201209
20120923
20121008
205
12/12/2012
3.3.0
3/6/14
8.2.1
done
201305
20130522
20130530
136
6/1/2013
3.3.1
3/6/14
8.2.1
done
201306
20130617
20130630
303
6/28/2013
3.3.1
3/6/14
8.2.1
done
201309
20130916
20130926
35
10/1/2013
3.3.1
3/6/14
8.2.1
done

201310

20131018
20131018
2
10/18/2013
3.3.1
3/6/14
8.2.1
done
201505 20150601 20150628
9
6/30/15
3.3.1
7/30/15
8.3.2

done

201510 20151024 20151103
55
11/4/15
3.3.1
11/9/15
8.3.2
done
201605 TBD TBD
175
         

Where green means 'done,' yellow means 'needs redoing to be on par' with latest, blue is 'in process,' red is 'to be done,' and purple means 'not yet scheduled or started'. The PPOL version number of DR1 was V7.1.0, while today's version is 8.3.2. The difference is in the size of the PSF fitting function, the degree of bad pixel repair, and some other minor bug fixes. The current BDP version is 3.3.1., and older version applications will need revisiting to assess whether to reprocess or not. [have found no need to reprocess via BDP - DPC]

** 2013/01/03 - The comparison between the results of PPOL 7.1.3 and 7.1.0 has been completed and several problems were fixed. A new/final version (PPOL 8.0) is being launched today. With it all GPIPS data will be reprocessed. As this processing is completed, final data will be released from this site.

Data Release Plan

GPIPS Data Release Plan Table
Data Release
Date Released
Fields Released
Notes
DR1 - 7.1.0
6/15/2012
578
Released
DR2 - 8.2.1
3/12/2014
All*
Released
DR3
12/4/2015
3,201
Released
DR4
8/1/2016
All
Planned

*DR2 was found to contain a small number of fields with substandard image quality and with large secular variations during data collection sequences. Many fields were reprocessed, some (see observations table above) were reobserved, and 36 fields were rejected using the new, tigher quality control criteria. DR3 is the release of the 'better' version of the DR2 data, though lacking the 36 fields that were rejected. DR4, planned for late summer 2016, will incorporate new observations of the 36 missing fields and reobservations of up to 139 fields whose image quality is far below the norm.

Data Collection Methodology

Image data were collected using the 1.8 meter Perkins telescope at Lowell Observatory and the wide-field imaging polarmetric mode of the near infrared instrument Mimir. In this mode, the field of view was 10'x10', and the plate scale was 0.58"/pixel. This system obtained significant polarization measurements for point sources down to about H=12th mag in about four minutes of total integration time.

Approximately 72 square degrees, between Galactic longitudes of 18 - 56 degrees and latitudes of -1 to +1 degree, were covered during the full course of the survey. This total area was covered by observing 3,237 overlapping Mimir fields of view toward centers located on a 9'x9' grid.

Based on the number of 2MASS stars with H-band magnitudes brighter than 12th mag, we estimate between 350,000 and 500,000 stars in the GPIPS region will have significant polarization detected.

Observing Methodology

Each of the 3,237 GPIPS fields took approximately 11-13 minutes of clock time to observe. At each field:

In addition, for almost every night GPIPS data were collected, we observed one or two fields of multiple polarization standard stars as well as a globular cluster located far off the Galactic plane, to serve as a field of polarization null stars.

During each observing run, polarization flat-fields were obtained using the lights-on/lights-off method against a flat-field screen located within the closed telescope dome. This was done only during a cloudy, moonless night so as to control all stray light sources. Additionally, because the InSb detector array was inherently non-linear in its response to light, we obtained a 50-100 illumination step set of images for the necessary linearity correction (see Clemens et al. 2007).

 


An image of Mimir attached to the Perkins telescope as it is during operation.

GPIPS Survey Status

Completion of GPIPS for the full 72 square degree area required observing a total of 3,237 fields and spanned the observing seasons 2006 - 2013.

In the figure below, the GPIPS field centers are displayed as black dots , the pilot survey fields are displayed as green diamonds, season one (2006) fields are displayed as open violet diamonds, and season two (2007) fields are displayed as open red diamonds.


The GPIPS region covers 72 square degrees ot the Galactic first quadrant midplane. This figure highlights fields observed in the first two seasons for GPIPS. The open green diamonds indicate the regions covered in the 2005 pilot study, 2006 season one fields are indicated with open violet diamonds, and open red diamonds show the fields taken during the 2007 second season. A larger, higher resolution version of the image can be obtained by clicking on the image.

Data Processing

There were three main stages of processing necessary to take raw Mimir image data to final stellar polarizations and images. These were: (1) basic image processing to take raw data to science-quality image form, (2) photometry of stars on science-quality images, and (3) combination of stellar photometry for the range of HWP angles to compute Stokes U and Q and convert these into polarization percentage and sky position angles. Included in each stage are all the necessay calibrations and corrections to recover true, outside-the-atmosphere, equatorially-true polarizations and position angles.

The software packages used to process Mimir data into GPIPS data products can be found at the Mimir Instrument Website Software Page

Details regarding the data processing may be found in Clemens et al. (2012a); calibration in Clemens et al. (2012b); and a summary of the properties of the data in the DR1 release (which are essentially identical to the DR2 final release) and the form of the data products are in Clemens et al. (2012c).