This page (revision-27) was last changed on 26-Oct-2022 21:57 by Peter Young

This page was created on 07-Jun-2010 19:35 by PeterYoung

Only authorized users are allowed to rename pages.

Only authorized users are allowed to delete pages.

Page revision history

Version Date Modified Size Author Changes ... Change note
27 26-Oct-2022 21:57 7 KB Peter Young to previous
26 07-Dec-2016 14:14 6 KB Peter Young to previous | to last
25 05-Apr-2011 18:14 6 KB PeterYoung to previous | to last
24 08-Jul-2010 15:42 6 KB PeterYoung to previous | to last
23 06-Jul-2010 16:15 7 KB PeterYoung to previous | to last
22 05-Jul-2010 10:39 7 KB ViggoHanst to previous | to last
21 03-Jul-2010 14:22 7 KB ViggoHanst to previous | to last

Page References

Incoming links Outgoing links
EISmethods
EISmethods

Version management

Difference between version and

At line 1 removed 2 lines
[{ALLOW edit EISMainUsers}]
[{ALLOW view Anonymous}]
At line 32 changed one line
To get the 1D wavelength array for the window, do:
!!Pointing coordinates (getxpos, getxcen, etc.)
At line 34 changed 2 lines
{{{IDL> wvl=data->getlam(iwin)
}}}
The heliocentric coordinates for the data are given by
At line 37 changed one line
although bear in mind that the spectra shift in the detector-X direction during an orbit, and in the Y-direction due to the tilt of the EIS slit relative to the detector. These issues are discussed in [EIS Software Note 5|http://solarb.mssl.ucl.ac.uk/SolarB/eis_docs/eis_notes/05_WAVELENGTH_CORRECTION/eis_swnote_05.pdf] and [EIS Software Note 4|http://solarb.mssl.ucl.ac.uk/SolarB/eis_docs/eis_notes/04_SLIT_TILT/eis_swnote_04.pdf], respectively.
{{{IDL> xpos=data->getxpos()
IDL> ypos=data->getypos()}}}
At line 39 changed one line
!!Pointing coordinates (getxpos, getxcen, etc.)
XPOS gives the X-coordinate for each slit position and YPOS gives the position for each pixel in the Y direction. The X-coordinate given includes the jitter (in X) that was recorded by the AOCS system, the pixel position given does not, but is rather based on the ycen at exposure '0'. In case the latter is desired for exposure 'n' then the (ycen(n)-ycen(0)) should be added to ypos(n) (see below).
At line 41 changed one line
The heliocentric coordinates for the center of a raster at a given wavelength, WVL, are obtained with:
In addition, the coordinates of the reference point used in the data object are given by
At line 43 changed 4 lines
{{{
IDL> xcen=data->getxcen(/raster)
IDL> ycen=data->getycen(wvl,/raster)
}}}
{{{IDL> xcen=data->getxcen()
IDL> ycen=data->getycen()}}}
At line 48 changed one line
More details about EIS pointing information are given on the wiki page [Obtaining pointing information from EIS data|EISPointing].
These points are defined to be the home position of the fine mirror in X, and the middle of the physical slit i Y. Note that this definition differs from that given in the FITS file header where XCEN and YCEN refer to the center of the raster (at the beginning of the observation). Thus, the center of the raster can be accessed by
At line 46 added 2 lines
{{{IDL> xcen=data->getinfo('XCEN')
IDL> ycen=data->getinfo('YCEN')}}}
At line 51 changed one line
!!Time routines
or, perhaps more reliably (especially as concerns older data), by taking the average of the extreme values given by the xpos and ypos methods.
At line 53 changed one line
!Exposure time
Note that each of these is an array of same size as the number of exposures. This is because the center of the raster moves with time due to the spacecraft jitter.
At line 55 changed one line
The exposure time (in seconds) for each exposure of the raster is given by
!!Exposure times and time routines
At line 55 added 2 lines
The exposure time for each exposure of the raster is given by
At line 60 changed one line
Note that the exposure times generally vary between exposures, and will not be exactly equal to the requested exposure time.
There are a number of other potentially useful methods to time related phenomena:
At line 62 removed 4 lines
!The start and end times of an exposure
The start and end times of an exposure can be obtained through the shutter open and close times (ti1 and ti2):
At line 70 changed one line
The units are given in TI format, which is the Hinode spacecraft time. The TI format can be converted to standard time formats using:
to find the shutter open (and close) times in 'TI' format.
At line 73 changed one line
IDL> utc=data->ti2utc(ti)
IDL> tai=data->ti2utc(ti)
At line 77 changed 8 lines
The last method gives the time in second since the start of the first exposure in the sequence.
NOTE: the difference between the shutter open and close times, and the exposure time returned by the getexp() method generally do not agree. The former being larger by a fraction of a second. There are various technical reasons for this including a latency between the Instrument Control Unit (ICU) communicating with the Mechanism & Heater Controller (MHC), and a delayed response time of the MHC. __Users are recommended to always use the exposure time returned by getexp().__
!Other time routines
The date of an observation can be obtained with various methods:
Convert 'TI' format time to atomic time units ('TAI') or UTC, if no 'ti' parameter is given, the shutter open (ti_1) times for the data object are converted. The final method 'SEC_FROM_OBS_START' computes the number of seconds from the start of observations given by the input array assumed to be in 'TI' format.
At line 91 changed one line
getdate_obs() gives the date in 'yyyy-mm-ddThh:mm:ss.sss' format, and getdate() in 'yyyymmdd' format. The date_obs2date converts the former to the latter format, if no date_obs is given the data object's date_obs is converted. days_since_launch() gives the number of days since launch, if no date is given then the data object's date is used.
Gives the date of obsvation in 'yyyy-mm-ddThh:mm:ss.sss' format ('GETDATE_OBS') or in 'yyyymmdd' format ('GETDATE'). The 'DATE_OBS2DATE' converts the former to the latter format, if no date_obs is given the data objects date_obs is converted. 'DAYS_SINCE_LAUNCH' gives the number of days since launch, if no date is given, the data objects date is used.
At line 117 changed 15 lines
The 'GETINFO' method can also be called by the eis data object to access the fits header fields, in which case there is no need to open the eis header object, just simply write
{{{IDL> date_obs=data->getinfo('DATE_OBS')
}}}
(The data object accesses the header object associated with it and returns the header information required)
!!Intensity units
To find the units for the intensity arrays in the data object, do
{{{IDL> units=data->getunit()}}}
which returns a 3-element string array, with the first element containing the intensity units. (The other elements are empty.)
The 'GETINFO' method can also be called by the eis data object to access the fits header fields, in which case there is no need to open the eis header object.
At line 143 changed one line
IDL> wp=cal->warm_pixels(data,iwin[0])}}}
IDL> wp=cal->warm_pixels(data,iwin)}}}
This page (revision-27) was last changed on 26-Oct-2022 21:57 by Peter YoungTop