AIA level1 data at
Extreme Ultraviolet, Ultra Violet and Visual wavelengths.
Four AIA telescopes are optimized to observe seven extreme ultraviolet (EUV) band passes centered on the following specific lines: Fe XVIII (94 Å), Fe VII/XXI (131 Å), Fe IX (171 Å), Fe XII, XXIV (193 Å), Fe XIV (211Å), He II (304 Å), and Fe XVI(335 Å) at a cadence of 12 seconds; two ultraviolet (UV) band passes centered at 1600 Å (C IV + continuum), and the continuum at 1700 Å at a cadence of 24 seconds; and, a ~500 Å FWHM band pass centered at 4500 Å. These 4069 x 4096 level 1 data images have undergone processing which includes bad-pixel removal, despiking and flat-fielding and can be found in the JSOC series aia.lev1.
The aia.lev1 data is further divided into three linked series to ease data retrieval:
- aia.lev1_euv_12s series points to the data from seven EUV filters at 94 Å,131 Å,171 Å, 193 Å, 211 Å, 304 Å, 335 Å taken at a cadenec of 12s.
- aia.lev1_uv_24s series points to data from the two UV band passes at 1600Å, 1700Å taken with a cadence of 24s.
- aia.lev1_vis_1h series points to the continuum data observed at ~4500 Å taken at a cadence of 1 hour.
Primary keywords for aia.lev1 data series is FSN (the Filtergram Sequence Number) and T_REC (the time of the observations).
The Primary Keywords for aia.lev1_euv_12s, aia.lev1_uv_24s and, aia.lev1_vis_1h data are T_REC and WAVELNGTH (Wavelength of observation in Angstroms). The WAVELNTH keyword (an integer) can be one of 335, 131 for camera 1; 193, 211 for camera 2; one of 171, 1600, 1700 or 4500 for camera 3, or 94, 304 for camera 4.
FITS header keywords for the AIA data are explained
WCS coordinate keyword descriptions can be found in this paper.
Algorithm For Calculation:
The raw telemetry data obtained from the AIA instrument is considered to be the Level 0 data. Processing Level 0 data to Level 1 involves the following steps:
- Removal of "over scan" rows and columns.
- Removal of a dark image to account for the digital offset of the camera, CCD read noise and dark current.
- Flat-field correction to account for detector non-uniformities, gain differences between CCD quadrants, vignetting and shadowing caused by focal plane filter nickel mesh.
- Correction to individual pixels using two algorithms is done. First to permanently correct "bad" pixels that do not respond correctly to light and second, to remove the "spikes" that appear as a result of the interaction of energetic particles that either deposit energy directly in the CCD, or interact with the instrument structure and give rise to high-energy photons that are detected in the CCD.
- The AIA images are flipped so as to put the solar North at the top of the array. The corresponding metadata are updated and additional information about the image and spacecraft housekeeping data (roll angle) is added.
- Note that these data are not exposure time corrected.
what about Level 1.5 data?
The link to the AIA pipeline processing is ??
The status of the JSOC pipeline processing can be checked here.
AIA calibration is described in detail in Boerner et al(2011)
. The calibration data are based on algorithms that are time dependant and include the camera gain, effective area, pointing information, bad-pixel list ,flat field, and average band pass effective area. As newer calibration data becomes available, Level 1 data can be reprocessed using the most recent calibration data.
Status Notes and/or Known Problems: