EOVSA Data products: Difference between revisions

From EOVSA Wiki
Jump to navigation Jump to search
 
(106 intermediate revisions by 3 users not shown)
Line 1: Line 1:
Welcome to the EOVSA data products documentation. EOVSA observes the full disk of the Sun at all times when the Sun is >10 degrees above the local horizon, which is season dependent and ranges from 7-12 hours duration centered on 20 UT. During January, coverage will be 16-24 UT daily, 7 days/week. EOVSA will provide microwave spectra and imaging at up to 451 frequencies between 1 and 18 GHz. We deliver the radio interferometry data in level 0-2.  
EOVSA observes the full disk of the Sun at all times when the Sun is >10 degrees above the local horizon (season dependent and ranges from 7-12 hours duration centered on 20 UT). EOVSA records data at 451 science frequency channels each second, in four polarization products, as well as additional total flux measurements from each individual antenna. Raw data in the visibility domain are processed through a pipeline processing system to produce images and spectrograms in the time- and frequency-dependent image plane (the block diagram in Figure 1 shows the data flow in the pipeline).  
[[File:pipeline_flowchart.jpg|center|600px]]
[[File:pipeline_flowchart.jpg|center|600px|EOVSA pipeline block diagram/flow chart ]]


=Data Definition=
We deliver the radio interferometry data on the following three levels:
==Level 0 - Raw visibility data from the instrument==


==Level 1 - Calibrated visibility data==
Level 1 data have all of the required content to produce Level 2 data products.
===[http://www.ovsa.njit.edu/fits/UDBms_slfcaled# CASA 1-min averaged ms]===
===CASA Event ms===


==Level 2 - Images and spectrogram data in standard FITS format ==
=Level 0 - Raw visibility data from the instrument=
===Data series===


====All-day TP spectrum====
As outlined in Figure 1, EOVSA creates raw data products in the left-hand column (labeled Level 0). This includes observations of cosmic sources for phase calibration, and gain and pointing observations required for total power calibration.
Daily total power full-Sun-integrated spectrogram calibrated in solar flux units are provided at 451 frequencies and 1 s time resolution.


<pre style="background-color: #FCEBD9;">
==Raw "Interim" Database (IDB) visibilities==
from suncasa.eovsa import eovsa_dspec as ds
Full-resolution raw "Interim" Database (IDB) visibility data. They are stored in Miriad format, and hence may not be that useful for most people. Be patient after clicking the link--this is a very long list of directories, one for each available date. These data can be retrieved from the following page:
## define the dynamic spectrum file.
 
tpfits = 'EOVSA_TPall_20191225.fts'
http://www.ovsa.njit.edu/fits/IDB/
## display the dynamic spectrum.  
ds.dspec(tpfits)
</pre>
[[File:TPSP.jpeg|center|500px]]


====All-day XP spectrum====
==Raw 1-min-averaged visibilities==
Daily cross power spectrogram (mean flux from baselines with "intermediate" lengths) calibrated in solar flux units are provided at 451 frequencies and 1 s time resolution. XP spectrogram has much better sensitivity to weak bursts.
This is the same as for the IDB data, except with 1-minute time integration applied. This is typically not useful for flares, but is perfectly fine for imaging active regions and full Sun. These data can be retrieved from the following page:


<pre style="background-color: #FCEBD9;">
http://www.ovsa.njit.edu/fits/UDB/
from suncasa.eovsa import eovsa_dspec as ds
## define the dynamic spectrum file.
tpfits = 'EOVSA_XPall_20191225.fts'
## display the dynamic spectrum.
ds.dspec(tpfits)
</pre>


[[File:XPSP.jpeg|500px| center]]
=Level 1.0 - Calibrated visibility data=
After applying calibration and other preliminary processing to level 0 data, we create the CASA ms’s in the second column in Figure 1 ( labeled Level 1). These visibility data have all of the required content to produce Level 2 images and spectrogram data in standard FITS format.  We provide a set of standard ms’s for each day (red boxes in Figure 1), for use by researchers who wish to start with visibility data.  


====Synoptic 6-band Images====
==Calibrated full-resolution visibility data for events==
Full disk images at 6 selected frequency bands centered at 1.4, 3.0, 4.5, 6.8, 10.2, and 13.9 GHz are provided once per day, calibrated in brightness temperature. [[File:synoptic_image.jpg| center |400px]]
EOVSA event data products in boxes with dashed outlines in Figure 1 will typically be available within 30 days after they are taken.


====10-min 6-band Images====
Link: TBD.
====Event images====


===Getting level 2 data===
==Self-calibrated 1-min-averaged visibility data==
EOVSA 1-min averaged visibility data in CASA ms format can be retrieved from the following page:


EOVSA Level 2 data products can be retrieved from the "synoptic data" page:
http://www.ovsa.njit.edu/fits/UDBms_slfcaled


[http://www.ovsa.njit.edu/fits/synoptic http://www.ovsa.njit.edu/fits/synoptic]
=Level 2.0 - Images and spectrogram data in standard FITS format =


Example - get the synoptic data on December 25, 2019
Most users, however, will prefer to work with spectrogram (frequency-time) and image data, which are also outputs of the pipeline system shown in Figure 1 (orange boxes). Spectrograms are provided as standard FITS tables containing the frequency list, list of times, and data in both total power and a sum of amplitudes over intermediate-length baselines (cross power). Likewise, image data products are in FITS format with standard keywords and are converted into the Helioprojective Cartesian coordinate system compatible with the World Coordinate System (WCS) convention, along with correct registration for the spatial, spectral, and temporal coordinates. Both the spectrogram and image data products are calibrated properly and have physical radio intensity units (sfu for spectrograms and brightness temperature for radio images).
* go to [http://ovsa.njit.edu/browser/ EOVSA browser] page.
* Browse to December 25, 2019.
* Click "synoptic fits" button next to the calendar tool.


List of Level 2 data products
'''List of Level 2 data products'''
{| class="wikitable"
{| class="wikitable"
|-
|-
Line 69: Line 50:
| EOVSA_XPall_yyyymmdd.fts
| EOVSA_XPall_yyyymmdd.fts
|-
|-
! rowspan="6" | Image
! rowspan="7" | Image
|-
|-
| Synoptic 1.4 GHz image
| Synoptic 1.4 GHz image
| eovsa_20191225.spw00-01.tb.disk.fits
| eovsa_yyyymmdd.spw00-01.tb.disk.fits
|-
|-
| Synoptic 3.0 GHz image
| Synoptic 3.0 GHz image
| eovsa_20191225.spw02-05.tb.disk.fits
| eovsa_yyyymmdd.spw02-05.tb.disk.fits
|-
|-
| Synoptic 4.5 GHz image
| Synoptic 4.5 GHz image
| eovsa_20191225.spw06-10.tb.disk.fits
| eovsa_yyyymmdd.spw06-10.tb.disk.fits
|-
|-
| Synoptic 6.8 GHz image
| Synoptic 6.8 GHz image
| eovsa_20191225.spw11-20.tb.disk.fits
| eovsa_yyyymmdd.spw11-20.tb.disk.fits
|-
|-
| Synoptic 10.2 GHz image
| Synoptic 10.2 GHz image
| eovsa_20191225.spw21-30.tb.disk.fits
| eovsa_yyyymmdd.spw21-30.tb.disk.fits
|-
|-
| Synoptic 13.9 GHz image
| Synoptic 13.9 GHz image
| eovsa_20191225.spw31-43.tb.disk.fits
| eovsa_yyyymmdd.spw31-43.tb.disk.fits
|}
|}


===Reading level 2 data===
==Getting level 2 data==
[[File:eovsa_browser.jpg|150px|thumb]]
EOVSA Level 2 data products can be retrieved with the following steps:
* go to [http://ovsa.njit.edu/browser/ EOVSA browser] page.
 
* Browse to the date of interest.
* Click "synoptic fits" button next to the calendar tool.
* Select the data product based on the names listed in the table above.
 
==Reading level 2 data==
===Software===
We have developed a package for EOVSA data processing and analysis:
[https://github.com/suncasa/suncasa SunCASA] A wrapper around [https://casa.nrao.edu/ CASA (the Common Astronomy Software Applications package)] for synthesis imaging and visualizing solar spectral imaging data. CASA is one of the leading software tools for "supporting the data post-processing needs of the next generation of radio astronomical telescopes such as ALMA and VLA", an international effort led by the [https://public.nrao.edu/ National Radio Astronomy Observatory]. The current version of CASA uses Python (2.7) interface. More information about CASA can be found on [https://casa.nrao.edu/ NRAO's CASA website ]. Note, CASA is available ONLY on UNIX-BASED PLATFORMS (and therefore, so is SunCASA). We are developing a new version of SunCASA based on CASA 6 (which offers a modular approach) so that users have the flexibility to build CASA tools and tasks in their Python environment.
 
Please [http://www.ovsa.njit.edu/wiki/index.php/SunCASA_Installation follow this link] for details regarding the installation of SunCASA on your own machine (only available on Unix-bases OS). This will take you to another page.
 
===All-day TP spectrum===
Daily total power full-Sun-integrated spectrogram calibrated in solar flux units are provided at 451 frequencies (134 frequencies prior to 2019 Feb 22) and 1 s time resolution. 
 
To read a spectrogram file in Python using the suncasa library:
 
<pre style="background-color: #FCEBD9;">
from suncasa.eovsa import eovsa_dspec as ds
from astropy.time import Time
from matplotlib.colors import LogNorm
## Read EOVSA Dynamic Spectrum FITS file <filename>
filename = 'EOVSA_TPall_20170713.fts'
s = ds.get_dspec(filename, doplot=True, cmap='gist_heat', norm=LogNorm(vmax=2.1e3, vmin=40))
## To access the data in the spectrogram object, use
spec = s['spectrogram']                    ## (Array of amplitudes in SFU, of size nfreq,ntimes)
fghz = s['spectrum_axis']                  ## (Array of frequencies in GHz, of size nfreq)
tim = Time(s['time_axis'], format='mjd')  ## (Array of UT times in astropy.time object, of size ntimes)
 
</pre>
 
The '''get_dspec''' function is accessible on [https://github.com/suncasa/suncasa-src/blob/master/suncasa/eovsa/eovsa_dspec.py GitHub]. For comprehensive guidance, please refer to suncasa's [https://suncasa-src.readthedocs.io/en/latest/autoapi/suncasa/eovsa/eovsa_dspec/index.html ReadtheDocs page].
[[File:TPSP.jpeg|center|500px]]
 
 
The following code will read the spectrogram file in IDL:
 
<pre style="background-color: #FCEBD9;">
function dspec,filename,doplot=doplot
  ; Read EOVSA Dynamic Spectrum FITS file <filename> and return a spectrogram object.
  ; Optionally show an overview plot if doplot switch is set
  ;
  ; Usage:
  ;    s = dspec(<filename>)            ; Returns spectrogram object
  ;    s = dspec(<filename>,/doplot)    ; Plots spectrum and returns spectrogram object
  ;
  ; To access the data in the spectrogram object, use
  ;    spec = s.get(/spectrogram)    (Array of amplitudes in SFU, of size ntimes, nfreq)
  ;    fghz = s.get(/spectrum_axis)  (Array of frequencies in GHz, of size nfreq)
  ;    ut = s.get(/time_axis)        (Array of UT times in anytim format, of size ntimes)
 
  default,doplot,0
  spec = mrdfits(filename,0)
  freq = mrdfits(filename,1)
  time = mrdfits(filename,2)
  fghz = freq.sfreq
  ut = anytim(time)
  s = spectrogram(spec,ut,fghz)
  if doplot then begin
    window,/free,xsiz=1024,ysiz=600
    ; Find min and max of data from 5% to 95% of sorted array (eliminates outliers)
    sarr = sort(spec)
    dlim = minmax(spec[sarr[n_elements(sarr)*0.05:n_elements(sarr)*0.95]])
    ; Set drange with margin factor of 2 on low end and 5 on high end
    s.set,drange=dlim*[0.5,5]
    loadct,3
    s.plot,/log,/xsty,/ysty,ytitle='Frequency [GHz]',charsize=1.5
  endif
return,s
end
</pre>
[[File:IDL_TPSP.png|center|500px]]
 
===Synoptic 6-band Images===
Full disk images at 6 selected frequency bands centered at 1.4, 3.0, 4.5, 6.8, 10.2, and 13.9 GHz are provided once per day, calibrated in brightness temperature. [[File:synoptic_image.jpg| center |400px]]
 
The EOVSA full disk image FITS files are compressed with the RICE algorithm implemented in the FITS file handling module (astropy.io.fits) in Astropy. EOVSA FITS files are very similar to the compressed SDO/AIA FITS files from JSOC. Popular coding languages can easily read compressed images directly.
 
In IDL, you can use read_sdo in the ONTOLOGY package, which should be installed by default in SolarSoftWare (SSW), to read compressed EOVSA FITS files. The following code will read the EOVSA image FITS file in SSWIDL:
 
<pre style="background-color: #FCEBD9;">
read_sdo,'eovsa_20191225.spw11-20.tb.disk.fits',header,data,/UNCOMP_DELETE
index2map,header,data,eomap
plot_map,eomap
</pre>
 
[[File:eovsa_20191225_image_sswidl.jpg| center |250px]]
 
In Python, you can use SunPy map module to read EOVAS FITS files. SunPy is an open solar data analysis environment for Python. The installation instruction can be found at [https://sunpy.org/ SunPy official website].
<pre style="background-color: #FCEBD9;">
import matplotlib.pyplot as plt
from sunpy import map as smap
eofile='eovsa_20191225.spw11-20.tb.disk.fits'
eomap = smap.Map(eofile)
eomap.plot()
plt.show()
</pre>
[[File:eovsa_20191225_image_py.jpg| center |250px]]
 
Although the Sunpy Python package already exists for doing analysis of solar data, it has a significant learning curve and lacks the generality of the Mapping routines written by Dominic Zarro for the IDL-based Solarsoft (SSW). We provided IDL Mapping routines available in Python that may help those IDL users who have been avoiding learning Python. '''The mapping routines work equally well in both Python 2.7 and Python 3'''.
Get the [http://www.ovsa.njit.edu/wiki/index.php/Mapping_Software Mapping routines]
The following code will read the EOVSA image FITS file in python:
<pre style="background-color: #FCEBD9;">
from mapping.plot_map import plot_map
from mapping.fits2map import fits2map
eofile='eovsa_20191225.spw11-20.tb.disk.fits'
eomap, h = fits2map(eofile,header=True)
plot_map(eomap, grid=15, limb=True,cmap='gray')
</pre>
[[File:eovsa_20191225_image_py_ssw-mapping.jpg| center |250px]]
 
===10-min 6-band Images===
===Event images===

Latest revision as of 15:47, 27 March 2024

EOVSA observes the full disk of the Sun at all times when the Sun is >10 degrees above the local horizon (season dependent and ranges from 7-12 hours duration centered on 20 UT). EOVSA records data at 451 science frequency channels each second, in four polarization products, as well as additional total flux measurements from each individual antenna. Raw data in the visibility domain are processed through a pipeline processing system to produce images and spectrograms in the time- and frequency-dependent image plane (the block diagram in Figure 1 shows the data flow in the pipeline).

EOVSA pipeline block diagram/flow chart

We deliver the radio interferometry data on the following three levels:


Level 0 - Raw visibility data from the instrument

As outlined in Figure 1, EOVSA creates raw data products in the left-hand column (labeled Level 0). This includes observations of cosmic sources for phase calibration, and gain and pointing observations required for total power calibration.

Raw "Interim" Database (IDB) visibilities

Full-resolution raw "Interim" Database (IDB) visibility data. They are stored in Miriad format, and hence may not be that useful for most people. Be patient after clicking the link--this is a very long list of directories, one for each available date. These data can be retrieved from the following page:

http://www.ovsa.njit.edu/fits/IDB/

Raw 1-min-averaged visibilities

This is the same as for the IDB data, except with 1-minute time integration applied. This is typically not useful for flares, but is perfectly fine for imaging active regions and full Sun. These data can be retrieved from the following page:

http://www.ovsa.njit.edu/fits/UDB/

Level 1.0 - Calibrated visibility data

After applying calibration and other preliminary processing to level 0 data, we create the CASA ms’s in the second column in Figure 1 ( labeled Level 1). These visibility data have all of the required content to produce Level 2 images and spectrogram data in standard FITS format. We provide a set of standard ms’s for each day (red boxes in Figure 1), for use by researchers who wish to start with visibility data.

Calibrated full-resolution visibility data for events

EOVSA event data products in boxes with dashed outlines in Figure 1 will typically be available within 30 days after they are taken.

Link: TBD.

Self-calibrated 1-min-averaged visibility data

EOVSA 1-min averaged visibility data in CASA ms format can be retrieved from the following page:

http://www.ovsa.njit.edu/fits/UDBms_slfcaled

Level 2.0 - Images and spectrogram data in standard FITS format

Most users, however, will prefer to work with spectrogram (frequency-time) and image data, which are also outputs of the pipeline system shown in Figure 1 (orange boxes). Spectrograms are provided as standard FITS tables containing the frequency list, list of times, and data in both total power and a sum of amplitudes over intermediate-length baselines (cross power). Likewise, image data products are in FITS format with standard keywords and are converted into the Helioprojective Cartesian coordinate system compatible with the World Coordinate System (WCS) convention, along with correct registration for the spatial, spectral, and temporal coordinates. Both the spectrogram and image data products are calibrated properly and have physical radio intensity units (sfu for spectrograms and brightness temperature for radio images).

List of Level 2 data products

category data product name
Dynamic Spectrum All-day TP spectrum EOVSA_TPall_yyyymmdd.fts
All-day XP spectrum EOVSA_XPall_yyyymmdd.fts
Image
Synoptic 1.4 GHz image eovsa_yyyymmdd.spw00-01.tb.disk.fits
Synoptic 3.0 GHz image eovsa_yyyymmdd.spw02-05.tb.disk.fits
Synoptic 4.5 GHz image eovsa_yyyymmdd.spw06-10.tb.disk.fits
Synoptic 6.8 GHz image eovsa_yyyymmdd.spw11-20.tb.disk.fits
Synoptic 10.2 GHz image eovsa_yyyymmdd.spw21-30.tb.disk.fits
Synoptic 13.9 GHz image eovsa_yyyymmdd.spw31-43.tb.disk.fits

Getting level 2 data

Eovsa browser.jpg

EOVSA Level 2 data products can be retrieved with the following steps:

  • Browse to the date of interest.
  • Click "synoptic fits" button next to the calendar tool.
  • Select the data product based on the names listed in the table above.

Reading level 2 data

Software

We have developed a package for EOVSA data processing and analysis: SunCASA A wrapper around CASA (the Common Astronomy Software Applications package) for synthesis imaging and visualizing solar spectral imaging data. CASA is one of the leading software tools for "supporting the data post-processing needs of the next generation of radio astronomical telescopes such as ALMA and VLA", an international effort led by the National Radio Astronomy Observatory. The current version of CASA uses Python (2.7) interface. More information about CASA can be found on NRAO's CASA website . Note, CASA is available ONLY on UNIX-BASED PLATFORMS (and therefore, so is SunCASA). We are developing a new version of SunCASA based on CASA 6 (which offers a modular approach) so that users have the flexibility to build CASA tools and tasks in their Python environment.

Please follow this link for details regarding the installation of SunCASA on your own machine (only available on Unix-bases OS). This will take you to another page.

All-day TP spectrum

Daily total power full-Sun-integrated spectrogram calibrated in solar flux units are provided at 451 frequencies (134 frequencies prior to 2019 Feb 22) and 1 s time resolution.

To read a spectrogram file in Python using the suncasa library:

from suncasa.eovsa import eovsa_dspec as ds
from astropy.time import Time
from matplotlib.colors import LogNorm
## Read EOVSA Dynamic Spectrum FITS file <filename>
filename = 'EOVSA_TPall_20170713.fts'
s = ds.get_dspec(filename, doplot=True, cmap='gist_heat', norm=LogNorm(vmax=2.1e3, vmin=40))
## To access the data in the spectrogram object, use
spec = s['spectrogram']                    ## (Array of amplitudes in SFU, of size nfreq,ntimes)
fghz = s['spectrum_axis']                  ## (Array of frequencies in GHz, of size nfreq)
tim = Time(s['time_axis'], format='mjd')   ## (Array of UT times in astropy.time object, of size ntimes)

The get_dspec function is accessible on GitHub. For comprehensive guidance, please refer to suncasa's ReadtheDocs page.

TPSP.jpeg


The following code will read the spectrogram file in IDL:

function dspec,filename,doplot=doplot
  ; Read EOVSA Dynamic Spectrum FITS file <filename> and return a spectrogram object.
  ; Optionally show an overview plot if doplot switch is set
  ; 
  ; Usage:
  ;    s = dspec(<filename>)            ; Returns spectrogram object
  ;    s = dspec(<filename>,/doplot)    ; Plots spectrum and returns spectrogram object
  ;
  ; To access the data in the spectrogram object, use
  ;    spec = s.get(/spectrogram)    (Array of amplitudes in SFU, of size ntimes, nfreq)
  ;    fghz = s.get(/spectrum_axis)  (Array of frequencies in GHz, of size nfreq)
  ;    ut = s.get(/time_axis)        (Array of UT times in anytim format, of size ntimes)
  
  default,doplot,0
  spec = mrdfits(filename,0)
  freq = mrdfits(filename,1)
  time = mrdfits(filename,2)
  fghz = freq.sfreq
  ut = anytim(time)
  s = spectrogram(spec,ut,fghz)
  if doplot then begin
    window,/free,xsiz=1024,ysiz=600
    ; Find min and max of data from 5% to 95% of sorted array (eliminates outliers)
    sarr = sort(spec)
    dlim = minmax(spec[sarr[n_elements(sarr)*0.05:n_elements(sarr)*0.95]])
    ; Set drange with margin factor of 2 on low end and 5 on high end
    s.set,drange=dlim*[0.5,5]
    loadct,3
    s.plot,/log,/xsty,/ysty,ytitle='Frequency [GHz]',charsize=1.5
  endif
return,s
end
IDL TPSP.png

Synoptic 6-band Images

Full disk images at 6 selected frequency bands centered at 1.4, 3.0, 4.5, 6.8, 10.2, and 13.9 GHz are provided once per day, calibrated in brightness temperature.

Synoptic image.jpg

The EOVSA full disk image FITS files are compressed with the RICE algorithm implemented in the FITS file handling module (astropy.io.fits) in Astropy. EOVSA FITS files are very similar to the compressed SDO/AIA FITS files from JSOC. Popular coding languages can easily read compressed images directly.

In IDL, you can use read_sdo in the ONTOLOGY package, which should be installed by default in SolarSoftWare (SSW), to read compressed EOVSA FITS files. The following code will read the EOVSA image FITS file in SSWIDL:

read_sdo,'eovsa_20191225.spw11-20.tb.disk.fits',header,data,/UNCOMP_DELETE
index2map,header,data,eomap
plot_map,eomap
Eovsa 20191225 image sswidl.jpg

In Python, you can use SunPy map module to read EOVAS FITS files. SunPy is an open solar data analysis environment for Python. The installation instruction can be found at SunPy official website.

import matplotlib.pyplot as plt
from sunpy import map as smap
eofile='eovsa_20191225.spw11-20.tb.disk.fits'
eomap = smap.Map(eofile)
eomap.plot()
plt.show()
Eovsa 20191225 image py.jpg

Although the Sunpy Python package already exists for doing analysis of solar data, it has a significant learning curve and lacks the generality of the Mapping routines written by Dominic Zarro for the IDL-based Solarsoft (SSW). We provided IDL Mapping routines available in Python that may help those IDL users who have been avoiding learning Python. The mapping routines work equally well in both Python 2.7 and Python 3. Get the Mapping routines The following code will read the EOVSA image FITS file in python:

from mapping.plot_map import plot_map
from mapping.fits2map import fits2map
eofile='eovsa_20191225.spw11-20.tb.disk.fits'
eomap, h = fits2map(eofile,header=True)
plot_map(eomap, grid=15, limb=True,cmap='gray')
Eovsa 20191225 image py ssw-mapping.jpg

10-min 6-band Images

Event images