DANGER!! ENTER AT YOUR OWN RISK!!
Effective area for Clear Filter:
defined as: (Mirror Reflectivity)*(Filter Transmission)*(QE)*(Aperature)
inputs: EIT processed (e.g. EIT_PREP) data to obtain either FeXII/FeIX,X or FeXV/FeXII ratio. Data can be whole images, single pixels, or vectors.
*Pre-flight Instrument Calibration- warning error source
/pre_calc option - use previously calculated spectra for speed
Please read header (doc_library,'eit_temp') for this routine
Example: Use the ratio of FeXII/FeIX,X to obtain the temperature and emission measure. The data chosen are a FeXII image taken on 7-Jul-1997 22:03:19 and a FeIX,X image on 7-Jul-1997 22:00:14. These are both subfields contained in the same Level zero file.
sswidl> eit_prep,'efz19970707.220014',hdr171,img171,image_no=0,/normalize,
/response
sswidl> eit_prep,'efz19970707.220014',hdr195,img195,image_no=2,/normalize,
/response
sswidl> temp_map = eit_temp(dn171=img171,dn195=img195,/pre_calc,dem=em_map)
sswidl> print,minmax(temp_map)
987684. 1.51475x1006
sswidl> print,minmax(em_map)
1.10257x1027 9.41696x1028
ISOTHERMAL: Calculate synthetic isothermal line spectra based upon synthetic in CHIANTI (units=photons s-1 sr-1 cm3 or ergs...).
CHIANTI_SPEC: Calculate synthetic isothermal spectra (units=photons s-1 sr-1 cm3 or ergs...). Shell routine around isothermal and conflx (this is a continuum flux routine written by J. Lemen based upon Mewe, Lemen, and van den Oord (Paper VI, 1986, A. A. Suppl., 65, 511.).
EIT_FLUX: EIT specific flux calculations:
Specify Te + filter + DEM ==> compute DN/s/pixel
Specify Te + filter + DN ==> compute DEM cm{-5} = INTEGRAL(N_e2)dh
where
e | electrons s-1 pixel-1 |
A | aperture area in cm2 |
apix | pixel area (cm2) |
T | transmission of aluminum filter(s) |
R | reflectivity of a single mirror |
f | telescope focal length in cm |
lam | wavelength in Angstroms |
q | CCD quantum efficiency (<= ~1.0) |
P | solar spectrum in photons cm-2 s-1 sr-1 |
A) Temperature calculations: 1) non-unique solutions 2) EIT relative response changes - we have an initial calibration, however this overcompensates any long term Solar trends 3) Line of Sight effects versus feature of interest - is background subtraction being used, source of error 4) We are just beginning to use cross checks with CDS NIS/GIS B) Emission measure calculations: 1) Instrument calibration: pre-launch values concerning: bandpass, mirror reflectivities, filter transmission, quantum efficiency 2) CCD response - time variability - physical changes?
Since EIT is sensitive to a narrow temperature range and of observations have 3 filters, the true temperature can have fairly good constraints.
No serious error analysis yet -> probably better than 1-2x105 K.