CCD and Digital Image Analysis

I have been working extensively on the digital image related analysis, including the hardware development (CCD), image based precision measurement, image quality control and digital imagery for google earth. Most of these are pretty technical and many of them are not published in Journals (well, too busy to wrote those papers and go through the review processes). I will introduce them in the following text and direct to the relevant website (google site) I created and maintained.

CCD & image based precision measurement.

The core part of the Dark Energy Survey project is to develop a new digital camera and use it at the Blanco telescope in Chile to take pictures of the night sky. The core part of the digital camera is the imager, consisting of a large array of red-sensitive CCDs (570 M pixels). You can read this to get more information and pictures about it: http://www.darkenergysurvey.org/DECam/DECam_add_tech.shtml

I am lucky to be in the team that develops this imager at Fermilab. My major work is to develop testing procedures and codes to check the quality of the CCD and images. I am also developing image based method to measure whether all the CCDs are on the same plane within an envelope of 60 microns. Here is a slide introduces my work and the project.

  • Hao, J., (2011), Dark Energy Survey Camera, Invited talk given at the DPF conference. [PDF]

Here is a paper I wrote to describe some of the work:

  • Hao, J., Estrada, J., Cease, H., Thomas Diehl, H., Flaugher, B. L., Kubik, D., Kuk, K., Kuropatkine, N., Lin, H., Montes, J., Scarpine, V, Schultz, K., & Wester, W. (2010). Measuring the Flatness of Focal Plane for Very Large Mosaic CCD Camera. Proc.SPIE Int. Soc. Opt. Eng., 7735: 77353U. [PDF]

A VERY COOL discovery I got with this method is the detection of one pixel (15 micron) offset of half of the CCD in the readout electronics, which is a remarkable proof of the usefulness of this method. Click here to see the details.

Here is a website I created to train the engineers/technicians: https://sites.google.com/site/decamtroubleshooting/home, where you can obtain the codes I wrote for analyze the images and the quality of the CCDs (Note that the repository has been moved to github from google project hosting)

Image quality control

To measure the astronomical object precisely, we need to make sure the image quality is good enough. Therefore, we need a set of standards to determine whether the quality is good. Also, based on the information we got from the image, we should be able to adjust the telescope system to improve the quality of the images. More details about this work can be found from this google site I created: https://sites.google.com/site/decamfocuscal/ . Here is a write-up describing the details concisely:

  • Hao, J., Bernstein, G., & Kent, S., Determine the alignment and focus of DECam based on the PSF distribution, [PDF]

Enhanced google earth imagery

I created an enhanced imagery for google earth so that people can hover the galaxy clusters in google earth (sky mode). I have a short description paper about this at: http://arxiv.org/abs/1010.6068 and a website about the imagery: https://sites.google.com/site/geclusters/.

I also create a site to show you the codes and steps to do this at: https://github.com/jgbrainstorm/des-google-earth

You can follow the reports in Wired Science and MIT technology review about my work.