Description of the NEAR EARTH ASTEROID TRACKING bundle V1.0 =========================================================== Bundle Generation Date: 2020-07-13 Peer Review: 2012 Asteroid Review, Wed May 30 00:00:00 MST 2012 Discipline node: Small Bodies Node Content description based on the data set catalog file description for the PDS3 version, EAR-A-I1063-3-NEAT-V1.0 ================================================================================================================ Note: for PDS3 data sets migrated to PDS4, the following text is taken verbatim from the data set description and confidence level note of the PDS3 data set catalog file. In these cases, some details may not be correct as a description of the PDS4 bundle. This dataset contains the Near-Earth Asteroid Tracking (NEAT) observations, associated darks, flats, log files and a list of Landolt standards. The data are archived in a series of volumes within the same data set. For a description of the individual volumes, see the aareadme.txt file at the root level of each individual volume. The images have been changed to fits format, but no image processing performed. Nightly, master (averaged) darks and sky-background images have been created for each night using standard IRAF software tools. A list of images used to create these calibration files are provided, although all the files reside with the original data under the obsdata sub-directory. Landolt standard stars (Landolt 1992) were not generally targeted during the survey. However, they did routinely fall on NEAT fields. A list provides the Landolt star, its position as listed from the Landolt catalog, its visual magnitude and the NEAT images with the field center and exposure time. Some fields were regularly observed, and these fields, if observed during the night, are included with the Landolt stars as potential calibration fields. SITE DESCRIPTION: NEAT began observations with the USAF 1.0m Ground-based Electro-Optical Deep Space Surveillance (GEODSS) telescope on Mt. Haleakala, Maui, HI (Pravdo 1999). In 2000, NEAT transitioned to the Maui Space Surveillance Site (MSSS) 1.2m telescope located at the same facility. The site is located at an elevation of 3040.35 meters and a latitude/longitude of +20deg 42.5'/156deg 15.5' west. The local time at the site is ten hours prior to Greenwich mean time. In 2001, the Palomar 1.2m Oschin Schmidt telescope located in northern San Diego, CA was incorporated into the NEAT inventory. The Oschin Schmidt is located at an elevation of 1726.3 meters, a latitude/longitude of +33deg 21.4'/116deg 51.8 west and is eight hours prior to GMT. CAMERA DESCRIPTION: The primary camera at the Maui site was a single 4096 x 4096 camera with 15 micron pixels. The pixel scale is 1.43 arc-sec/ pixel with the 1.0m GEODSS telescope and 1.36 arc-sec/pixel with the MSSS 1.2m. No filters were used and the bandpass is 0.4 - 0.8 microns, however the peak response matches closely with the Bessel-type R filter at 0.6 microns. A thermoelectric cooler (TEC) maintains an approximate operating temperature of -5 and -20 degrees C for the GEODSS and MSSS cameras, respectively. Four amplifiers readout the CCD in four quadrants. The Palomar 'Tri-camera' consists of three separate 4096 x 4096 pixel CCDs. The CCDs are arranged in a linear, north-south, orientation and denoted by 'A, B or C.' An approximate one-degree gap is between each CCD and each covers nearly 1.0 square degree. The 15 micron pixels yield a pixel scale of 1.01 arc-sec/pixel. As with the Maui system, no filters were used, but matches closely with a Bessel-type R filter at 0.6 microns and TECs maintained an operating temperature of approximately -30 degrees C. Four amplifiers readout the CCD in four quadrants. See tables 1 and 2 for instrument and site summary. These two cameras used 'CCD485' chips produced by Fairchild Imaging. The central wavelength is 702 nm. ---------------------------------------------------------- | Site Maui/GEODSS Maui/MSSS | | Dates of Operation: 12/95 - 2/99 2/00 - 4/07 | | Telescope Diameter: 1.0m 1.2m | | f/ratio: 2.15 3.14 | | Camera: 4096 x 4096 4096 x 4096 | | Pixel Size: 15 x 15 u 15 x 15 u | | Pixel Scale: 1.43'/pix 1.36'/pix | | Cooling: TEC @ ~-5C TEC @ ~-20C | | Filter: None None | | IAU Site Code: 566 608 | | Latitude / Longitude: +20deg 42.5' 156deg 15.5'W | | Elevation / Timezone: 3040.35m UTC - 10 | |________________________________________________________| Table 1 - A comparison of telescopes and instruments used by NEAT on Mt. Haleakala, Maui, HI -------------------------------------------------------------- | Site Pal/Tri-cam Palomar/QUEST | | Dates of Operation: 4/01 - 6/03 6/03 - 4/07 | | Telescope Diameter: 1.2m 1.2m | | f/ratio: 2.50 2.50 | | Camera: 4096 x 4096 x 3 600 x 2400 x 112 | | Pixel Size: 15 x 15 u 13 x 13 u | | Pixel Scale: 1.01'/pix 0.87'/pix | | Cooling: TEC @ ~-30C LN2 @ -120C | | Filter: None 610 nm | | IAU Site Code: 644 644 | | | | Latitude / Longitude: +33deg 21.4' 116deg 51.8'W | | Elevation / Timezone: 1726.3m UTC - 8 | |____________________________________________________________| Table 2 - A comparison of the instruments used by NEAT at Palomar Observatory. The QUEST camera began operations at Palomar Observatory in June 2003 and replaced the tri-camera (Baltay 2007). It was designed and constructed at Yale University and consists of 112 CCD chips manufactured by the Sarnoff corporation. Four rows, or fingers, each contain twenty-eight CCDs. Each CCD is 600 x 2400 with 13 micron square pixels. The pixel scale is 0.87 arc-sec/pixel. The camera covers an area of 4.6 degrees by 3.6 degrees with an effective area of 9.6 square degrees of sky. The central wave- length is 760 nm. During the point-and-track observations used by NEAT, a red (effective wavelength 610 nm) Bessel filter was used. The fingers are symmetrical about the bore sight. As a result, the pointing centers listed in the logs are the pointing centers of the bore sight; not CCD chip centers. Fingers B and C are offset from the bore sight by +/-30.07 arc-secs (0.5012 deg.) while fingers A and D are offset by +/-90.17 arc-secs (1.5028 deg.), respectively. The twenty-eight CCDs are laid out in an North-South orientation (chips 01-28) from +/-2.25 degrees (chips 01 - 28) from the bore sight pointing coordinates (see table 3). Finger CCD D C RA RA DEC 01 -1.5028 -0.5012 2.2483 02 -1.5028 -0.5012 2.0819 03 -1.5028 -0.5012 1.9155 04 -1.5028 -0.5012 1.7490 05 -1.5028 -0.5012 1.5826 06 -1.5028 -0.5012 1.4160 07 -1.5028 -0.5012 1.2495 08 -1.5028 -0.5012 1.0829 09 -1.5028 -0.5012 0.9164 10 -1.5028 -0.5012 0.7498 11 -1.5028 -0.5012 0.5832 12 -1.5028 -0.5012 0.4166 13 -1.5028 -0.5012 0.2499 14 -1.5028 -0.5012 0.0833 15 -1.5028 -0.5012 -0.0833 16 -1.5028 -0.5012 -0.2499 17 -1.5028 -0.5012 -0.4155 18 -1.5028 -0.5012 -0.5832 19 -1.5028 -0.5012 -0.7498 20 -1.5028 -0.5012 -0.9164 21 -1.5028 -0.5012 -1.0829 22 -1.5028 -0.5012 -1.2495 23 -1.5028 -0.5012 -1.4160 24 -1.5028 -0.5012 -1.5826 25 -1.5028 -0.5012 -1.7490 26 -1.5028 -0.5012 -1.9155 27 -1.5028 -0.5012 -2.0819 28 -1.5028 -0.5012 -2.2483 -------------------------------- Table 3: QUEST CCD chip offsets for fingers C and D. Fingers B and A are mirror copies and consist of the same, positive, values (ie finger B's RA offset is 0.5012 degrees and A's RA offset is 1.5028 degrees). IMAGE DESCRIPTION: Regardless of the camera, each CCD chip read to a unique output file. Filenames are based on the universal start time of the exposure and, if appropriate, identify the specific chip used. The Maui and tri-camera images contain the 4080 x 4080 imaging area. Because the NEAT survey was interested in astrometry and not photometry, the data are not bias corrected, nor were the bias saved. Within the QUEST data, however, the overscan regions are available in the 40 extra rows (rows 600-640). The initial orientation of the Maui and Palomar tri-camera images has East towards to left and North downward. Each uncompressed, 4k x 4k, (Palomar tri-camera and Maui) image is 66.6 and 33.3 Mb in size, respectively. The QUEST images are 3.1 Mb in size, uncompressed, with North towards the left and West downward initially. OBSERVING STRATEGIES: NEAT concentrated its observations to the ecliptic with highest priority to opposition. The Palomar and Maui sites worked in conjunction with each other and rarely observed identical search fields on the same night. The same follow-up field may have been taken by both telescopes to assure acquisition of newly discovered NEAs. The NEAT detection software required three observations at the same location. These 'triplets' were obtained with revisit or cadence times between fifteen to thirty minutes. Integration times were, typically, 20 seconds at the Maui site and 60 seconds at Palomar. However, it was not uncommon to vary exposure times to 120 and/or 150 seconds at Palomar. When NEAT began observations with the Maui camera, integration times varied from 40 seconds to 60 seconds. Two log files list the RA and DEC, in J2000 coordinates, in sexagesimal format and decimal of degrees, the integration times and filenames. The 'log dot group' file (filenames in the format of YEARMMDD_log_group.tab) displays the approximate cadence time between revisits and the files associated with a particular RA/DEC and the closest dark frame obtained prior to the observation. These log files are in the following format: Center of chip Center of Chip Apprx. Sexagesimal Decimal of Deg Shtr Bin Cadnce No. & List RA DEC RA Dec Opn? fctr Exp Time of Images hh mm ss dd mm ss deg deg y/n 1 (sec) (sec) Similarly, the 'log dot obs' file (usually with a filename in the format of YEARMMDD_log_obs.tab) lists every image obtained with its associated RA and DEC (J2000) and integration time. The 'log dot obs' files are formatted as the following: Center of chip Center of Chip Sexagesimal Decimal of Deg Shutter Bin Image RA DEC RA Dec Open? factor Exp Filename hh mm ss dd mm ss deg deg y/n 1 (sec) Within the header of each image, the chip center in sexagesimal format (hour and degrees, minutes and seconds) are clearly labeled. In addition, these RA and DEC values are listed in degrees under the 'CRVAL1' and 'CRVAL2' keywords, respectively. These are for reference only and do not represent the center's astrometric solution. Nearly all of the data is binned 1x1 and only the darks respond 'n' to the shutter question. There are a few, rare, occasions when the data was binned 2x2. FILE AND DIRECTORY NAMING CONVENTION: The data file and directory naming conventions vary by instrument. This is documented further in the aareadme.txt file for that instrument's volume. All data subdirectories have the same internal directory structure. All image files reside under the 'obsdata' subdirectory. Darks and flats are stored under their respective names. A file containing the list of Landolt standards observed resides under the 'landolts' subdirectory. The log files are kept under the 'logs' subdirectory. NEAT was nearly an autonomous system and was chartered to operate with little disruption to on-site personnel. Observing log files for each site have been maintained with filenames in the format of SITE_nightly_log (with SITE equal to Pal (for Palomar data - both QUEST and the tri-camera) and MS3 (for the Maui data - both GEODSS and MSSS)). However, the observing logs stating the nightly sky conditions are brief. At times, Air Force personnel at the Maui site made generic comments about the nightly observing conditions. It is not uncommon for no comments to be made. Conversely, the Palomar log, Pal_nightly_logPDSdelivery2.pdf, contains notes on the weather conditions and seeing as reported by the 200-inch telescope operator. Note, this is the weather reported at the 200-inch. Although the 48-inch, Oschin Schmidt is not far away, it may be effected by slightly different weather and seeing. Entries include cloud cover, relative humidity and wind speed, as well as the seeing. PROCESSING: Limited processing has been applied to the data. All data have been changed from a unique NEAT format to a generic fits format. All headers have been modified to agree to the PDS' formats and standards. Additional information for each observation has been determined including the air mass (SECZ) and readnoise (READN). REFERENCES: Baltay, C., D. Rabinowitz, P. Andrews, A. Bauer, N. Ellman, W. Emmet, R. Hudson, T. Hurteau, J. Jerke, R. Lauer, J. Silge, A. Szymkowiak, B. Adams, M. Gebhard, J. Musser, M. Doyle, H. Petrie, R. Smith, R. Thicksten, J. Geary, 'The QUEST Large Area CCD Camera,' PASP 119 (2007), pp. 1278--1294. Landolt, A.U., 1992, UBVRI photometric standard stars in the magnitude range 11.5-16.0 around the celestial equator. Astron. J. 104, 340-371. Pravdo, S. H., E. F. Helin, D. L. Rabinowitz, K. J. Lawrence, R. J. Bambery, C. C. Clark, S. L. Groom, S. M. Levin, J. J. Lorre, 'The Near-Earth Asteroid Tracking (NEAT) Program: An Automated System for Telescope Control, Wide-Field Imaging, and Object Detection', Astronomical Journal 117 (1999), pp. 1616-1633. Known issues or problems with the data ====================================== ANOMALIES: Like all ground-based observations, the data is effected by local weather and atmospheric conditions. In addition, telescope guiding, focus and hardware problems can further degrade the data. Frost and condensation have appeared periodically on the camera window, especially on the Maui data. All data, except the QUEST data, are obtained from multi-amplifer detectors. As such, each quadrant (1024 x 1024 pixels) is subject to gain and bias offset anomalies and may not be persistent across the entire field or throughout the night. Consequently, the calibration frames may not compensate for these anomalies of the individual frames and it is left to the user to correct. Six QUEST CCDs were bad and un-operational. These were chips A10, A15, B01, B07, C06, D07. Others performed intermittently and have been noted and identified in the 'dead.txt' file under the logs subdirectory . Other chips are affected with bad columns, moire patterns, amplifier glow and LED glow. The log files are for reference only and do not represent the centers' astrometric solution. PDS3 Source =========== Version 1.0 of this bundle was migrated from version 1.0 of the PDS3 data set EAR-A-I1063-3-NEAT-V1.0.