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 added 2 lines
[{ALLOW edit EISMainUsers}]
[{ALLOW view Anonymous}]
At line 30 changed one line
!!Pointing coordinates (getxpos, getxcen, etc.)
To get the 1D wavelength array for the window, do:
At line 32 changed one line
The heliocentric coordinates for the data are given by
{{{IDL> wvl=data->getlam(iwin)
}}}
At line 34 changed 2 lines
{{{IDL> xpos=data->getxpos()
IDL> ypos=data->getypos()}}}
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.
At line 37 changed one line
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).
!!Pointing coordinates (getxpos, getxcen, etc.)
At line 39 changed one line
In addition, the coordinates of the reference point used in the data object are given by
The heliocentric coordinates for the center of a raster at a given wavelength, WVL, are obtained with:
At line 41 changed 2 lines
{{{IDL> xcen=data->getxcen()
IDL> ycen=data->getycen()}}}
{{{
IDL> xcen=data->getxcen(/raster)
IDL> ycen=data->getycen(wvl,/raster)
}}}
At line 44 changed one line
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
More details about EIS pointing information are given on the wiki page [Obtaining pointing information from EIS data|EISPointing].
At line 46 removed 2 lines
{{{IDL> xcen=data->getinfo('XCEN')
IDL> ycen=data->getinfo('YCEN')}}}
At line 49 changed one line
or, perhaps more reliably (especially as concerns older data), by taking the average of the extreme values given by the xpos and ypos methods.
!!Time routines
At line 51 changed one line
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.
!Exposure time
At line 53 changed one line
!!Exposure times and time routines
The exposure time (in seconds) for each exposure of the raster is given by
At line 55 removed 2 lines
The exposure time for each exposure of the raster is given by
At line 60 changed one line
There are a number of other potentially useful methods to time related phenomena:
Note that the exposure times generally vary between exposures, and will not be exactly equal to the requested exposure time.
At line 62 changed one line
{{{IDL> ti=data->getti_1()
!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):
{{{IDL> ti1=data->getti_1()
IDL> ti2=data->getti_2()
At line 65 changed one line
(also getti_2) to find the shutter open (and close) times in 'TI' format.
The units are given in TI format, which is the Hinode spacecraft time. The TI format can be converted to standard time formats using:
At line 67 changed 2 lines
{{{IDL> ti=data->getti_1()
{{{IDL> tai=data->ti2tai(ti)
IDL> utc=data->ti2utc(ti)
IDL> sec=data->sec_from_obs_start(ti)
At line 71 changed 7 lines
function eis_data::getdate,init=init
if n_elements(init) eq 1 then return, -1
dum=strsplit(self->getfilename(),'/',/extract)
filename=dum[n_elements(dum)-1]
date=(strsplit(filename,'_',/extract))[2]
return,date
end
The last method gives the time in second since the start of the first exposure in the sequence.
At line 79 changed 5 lines
function eis_data::date_obs2date,date_obs
if n_elements(date_obs) eq 0 then date_obs=self->getdate_obs()
date=strmid(strjoin(strsplit(date_obs,'-T:',/extract),''),0,8)
return,date
end
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().__
At line 85 changed 4 lines
function eis_data::getdate_obs,init=init
if n_elements(init) eq 1 then return, -1
return,(self->gethdr())->getdate_obs()
end
!Other time routines
At line 90 changed 6 lines
function eis_data::days_since_launch,date
if n_elements(date) eq 0 then date=self->getdate_obs()
jd_date=(anytim2jd(date)).int
jd_launch=(anytim2jd((self->getcal())->getlaunch_date())).int
return,jd_date-jd_launch
end
The date of an observation can be obtained with various methods:
At line 97 changed 6 lines
function eis_data::ti2tai,ti,init=init
; time ti, ICU in mdp units of 1/512 s, converted to atomic time units (tai) (sort of....)
if n_elements(init) eq 1 then return, -1
if n_elements(ti) eq 0 then ti=*(self->getaux_data()).ti_1
return,anytim2tai(self->getinfo('date_obs'))+self->sec_from_obs_start(ti)
end
{{{IDL> date_obs=data->getdate_obs()
IDL> date=data->getdate()
IDL> date=data->date_obs2date(date_obs)
IDL> days=data->days_since_launch(date)
}}}
At line 104 changed 7 lines
function eis_data::ti2utc,ti,init=init
if n_elements(init) eq 1 then return, -1
if n_elements(ti) eq 0 then ti=*(self->getaux_data()).ti_1
return,anytim2utc(self->ti2tai(ti),/time_only,/ccsds,/truncate)
end
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.
At line 112 added 20 lines
Any field in the fits header can also be accessed easily by using, i.e. the above can be performed by typing
{{{IDL> date_obs=hdr_obj->getinfo('DATE_OBS')
}}}
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.)
At line 141 changed one line
IDL> wp=cal->warm_pixels(data,iwin)}}}
IDL> wp=cal->warm_pixels(data,iwin[0])}}}
At line 175 added 6 lines
You can also view a 'quick and dirty' map from the data object 'd' directly via,
{{{IDL> mmap=d->mk_eis_map(195.12)}}}
This will give an intensity map computed by summing in wavelength the pixels in the spectral window.
This page (revision-27) was last changed on 26-Oct-2022 21:57 by Peter YoungTop