A Comparison of Lunar Images from Clementine and Lunar Orbiter to Search for New Surface Features or Craters The Lunar Surface: Visualizing Changes A Comparison of Lunar Images from Clementine and Lunar Orbiter to Search for New Surface Features or Craters Chitra Sivanandam, Roger Easton, Zoran Ninkov Center for Imaging Science Rochester Institute of Technology May 8, 1998

Chitra SivanandamSenior Research: May 8, 1998 Outline  Introduction  Proposed Objectives  Accomplished Tasks/Results  Analysis  Conclusion

Chitra SivanandamSenior Research: May 8, 1998 Introduction  Lunar Orbiter Imagery  Higher Resolution (scan from a contact print)  Better ground resolution  Do not have as much information on how the image was taken exact latitudes and longitudes exact latitudes and longitudes angle of the photograph angle of the photograph

Chitra SivanandamSenior Research: May 8, 1998 Introduction cont’d  Clementine Imagery  Lower resolution, both in ground spot and in image resolution  PDS format  Have much information on the specifics pertaining to imagery latitudes, longitudes, angle, etc. latitudes, longitudes, angle, etc. limited bandwidth (sensor) compared to sensitivity of film limited bandwidth (sensor) compared to sensitivity of film

Chitra SivanandamSenior Research: May 8, 1998 Proposed Objectives  Create a tool to use both sets of images  Try to account for differences in imagery that do not translate to differences in the surface  Look for any differences in the surface that may have occurred as a result of time

Chitra SivanandamSenior Research: May 8, 1998 Accomplished Tasks/Results  Created a procedure using NasaView (for Clementine images), Erdas Imagine, Photoshop and code written in IDL  NasaView - to chose an appropriate section of the 16bits to use  Photoshop - convert images to tiff format  Imagine - used the GCP (ground control points) editor to create a transform to resample images  IDL - to do the differencing

Chitra SivanandamSenior Research: May 8, 1998 Accomplished Tasks/Results cont’d  Using IDL, created a tool to do differencing trying to account for various problems with imagery (using test images)

Chitra SivanandamSenior Research: May 8, 1998 Accomplished Tasks/Results cont’d  After doing the resampling and transformation, applied the code to images  Major differences occurred because the Orbiter image was of a much higher resolution than the Clementine image  Chose to use a low pass filter  Invested the use of a Robert’s gradient for edge detection prior to differencing

Chitra SivanandamSenior Research: May 8, 1998 Accomplished Tasks/Results cont’d Lunar Orbiter image Using a low pass filter Clementine image

Chitra SivanandamSenior Research: May 8, 1998 Accomplished Tasks/Results cont’d  Low Pass filter  Gaussian Filter, with a weight of 121

Chitra SivanandamSenior Research: May 8, 1998 Accomplished Tasks/Results cont’d Robert’s Gradient of Orbiter image of low pass image

Chitra SivanandamSenior Research: May 8, 1998 Accomplished Tasks/Results cont’d Robert’s Gradient for Clementine image

Chitra SivanandamSenior Research: May 8, 1998 Accomplished Tasks/Results cont’d Difference simply between images Difference using the low pass image

Chitra SivanandamSenior Research: May 8, 1998 Accomplished Tasks/Results cont’d Resultant images using the Robert’s gradient / edge detection before actual differencing

Chitra SivanandamSenior Research: May 8, 1998 Analysis  Smaller, higher frequency differences do not show up as much when using the low pass filter  Overall differences due to the histograms of the images are taken care of by doing an edge detection

Chitra SivanandamSenior Research: May 8, 1998 Analysis cont’d  What is causing all of the differences?  Most of the features from the difference images exist in the Orbiter image  Most of the difference seems to be due to the differences in image resolution  The bulk of the differences is due to the illumination angle at the time the images were taken

Chitra SivanandamSenior Research: May 8, 1998 Conclusion  It is possible to create a tool to work with both sets of imagery  It would be more useful if the images have something in common (i.e. ground resolution).  There were too many differences between the imagery.  Basically, the region immediately near the crater Aristarchus does not seem to have changed over the last 30 years.

Chitra SivanandamSenior Research: May 8, 1998 THE END