Tutorial: Using SDO Solar Data

[Drop Of Sun]

Hi,

Here's a tutorial on how to get going with downloading and processing SDO solar data (4096x4096 full disc, 16 bit mono) for non-commercial use. There seem to be many clever ways to access the data, they are over my head unfortunately. This is my fools guide Please add your better ways below. Also, please add your first processed image if you like! I hope you have fun exploring this amazing data! Thanks to the amazing folks at NASA/SDO.

---

 

USING SDO DATA TUTORIAL

1. Copyrights

Please include a credit to NASA/SDO in your processed images. From the SDO site:

SDO images and movies are not copyrighted unless explicitly noted. The use of SDO images for non-commercial purposes and public education and information efforts is strongly encouraged and requires no expressed authorization. It is requested, however, that any such use properly attributes the source of the images or data as:
"Courtesy of NASA/SDO and the AIA, EVE, and HMI science teams."

http://sdo.gsfc.nasa.gov/data/rules.php

 

2. Using Helioviewer

SDO has a lot of solar data! First, find out what time, date and wavelengths you want using Helioviewer:

http://helioviewer.org/

 

The Measurement dropdown is where you can choose the wavelength (see image below). So far, I particularly like AIA 171 (cool magnetic lines), 304 (a bit like h-a) and 1700 (looks like CaK to me).

 

3. Downloading your data from the Virtual Solar Observatory (VSO)

There appear to be many interfaces to the data. This way is using the Virtual Solar Observatory (VSO).

Go straight to the VSO Time Search Form:

sdac.virtualsolar.org/cgi/search?time=1&version=curre...

Or for general VSO info, go here:

sdac.virtualsolar.org/cgi/search

(From this general page, clicking on 'Generate VSO Search Form' takes you to the VSO Time Search form.)

 

On the VSO Time Search Form:

Set the Start Date/Time to the date/time you got from Helioviewer (I hope you chose a suitably massive prom!!)

Set the End Date/Time to one minute later than the Start Date! I am just after single images, so I don't want a massive list of hours of data, one minute should give me at least one image in the various wavelengths I want.

Click the Search button and wait a few moments while VSO has a think. Give it time. It has to send the solar telescope back in time to when you want, capture your data, send it back to the present, and give you access to the data. Time travel takes time.

 

The results page should appear. If you see a little status window appear that says 'VSO-D503 Unavailable - Not able to access NGDC at this time. We are working on a solution.' - close that little window (don't close the Results page, just the little status window!).

Click on 'Long' in the Views section to the right, above the main list:

 

You should now see more info (a long list!):

Scroll down the list and keep an eye out for the wavelengths you want (e.g. 131, 171, 304, 1700) and check that the filesize for these is 66200. These should be 4096x4096 16 bit mono fits files.

Check the box for each file that you want to download. Then click the 'Request Data' button.

You are then asked to select your transfer method:

Set 'Select Transfer Method' to  "URL-FILE" and click 'Request Data'.

Wait a few moments for SDO to return your list of data download links (listed under 'Comments'):

Click on a link.

Nearly there! You should see a dialog appear that allows you to open or save the image:

Note that after you have installed Fits Liberator later on, this dialog may default to opening the file in that program.

Choose Save File and click OK to save your file.

Click on the other files in your download list one by one and save them likewise.

 

3. Using Fits Liberator

Download and install Fits Liberator from:

www.spacetelescope.org/projects/fits_liberator/

This program is used for converting fits files to TIF. And it has a cool space logo!

When you first run it you will see an Open dialog. Use it to open your file.

Here I've opened AIA171 data:

Notice in the histogram below the solar image there are two vertical lines, these are clipping the data. In the solar image you are seeing all the tones between these two vertical lines. Tones left of the left bar are clipped to black, tones to the right of the right bar are clipped to white.

Drag the left and right vertical lines in the histogram below the solar image to the far left and far right respectively to prevent clipping of the image, so that darks are not underexposed and whites are not overexposed in your exported file:

Click 'Save File' and save your 16-bit TIF.

 

4. First steps in Photoshop

Open the TIF file in Photoshop.

Choose "Image > Adjustments > Curves." Apply curves one or a few times to reveal the data roughly how you would like:

Wohoo! I think you'll agree, NASA/SDO did the hard work.

If you want to lay down some base colours, in Photoshop choose "Image > Mode > RGB Color":

 

To add false colour, a good starting point can be a gradient map (Image > Adjustments > Gradient Map):

 

From here, further process to taste. I enjoyed trying to bring out a little more detail in the loops:

 

I hope you found this useful. Have fun!

A big thanks to NASA/SDO.

Edited February 13, 2016 by Drop Of Sun

[Drop Of Sun]

The tutorial shows downloading of Level 1 data. Here's some info on what Level 1 data means:

http://jsoc.stanford.edu/new/AIA/AIA_lev1.html

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.

[David Smith]

Wow great write up Luke. I will still be imaging but I am looking forward to seeing your work on this project.

[Pete Presland]

Some interesting techniques explained there, beats cloud watching! 

[GreatAttractor]

Thanks for all the information. I've just created me a nice wallpaper using one of the 4096x4096 AIA 171 images.

Turned out ImPPG required a small fix to accept some of the FITS files (they have two images inside, the first has size 0, the second one is the actual picture).