The Caves of Copernicus

Copernicus wrote:I'd be quite interested in seeing the image of "E" that you mentioned, LCG. I don't believe that I missed a NAC, but I may have... and I've looked at all of the ones of "E" that are available.

Copernicus wrote:Here’s the latest image of James’ Pit H1 just uploaded a few days ago…



This is the highest res of it yet.

C

rick1959 wrote:Creepy how?

The top two got me interested in its lunar sky light characteristic of a curved lit portion at a lower level. The third image added to the cavelike jump aspect to a lower level. But the last two images show a continuous surface for both of these, meaning the feature is likely only a crater or collapse sinktype feature filled with dust of various grades.

Pixel scale (m/pixel) is a convenient way to describe a camera's ability to capture feature details on the lunar surface, although strictly speaking it takes 2-4 pixels to resolve an object. Perhaps the simplest value to start with when describing image resolution is the pixel scale defined as the size of a pixel projected onto the ground. In the case of the LROC Narrow Angle Cameras (NACs) the angular scale of a single pixel is only 0.000572958°, which from an altitude of 100 km provides a ground scale of 1.0 meter per pixel. However, the true resolution is always poorer than the ground scale.

First, the optics and the CCD introduce scatter to some of the incoming light, which works to slightly blur the image. Next, in the case of the NACs, the pixels move across the ground as the exposure is made introducing along-orbit smear. Finally, the image quality is affected by the illumination of the scene. When the Sun is near noon and the ground is brightly illuminated, the signal received by the camera is strong. When near sunset or sunrise, the scene is poorly illuminated and signals are weak. A handheld camera can usually compensate for low light levels with a flash – if not, you will see a grainier image.

For the five Apollo landing sites imaged by LROC, the biggest variables are spacecraft altitude (ground scale) and time of day, which translates into signal strength. In the current collection of images the best feature discrimination is in the Apollo 14 scene (astronaut tracks and ALSEP) even though the highest resolution picture covers the Apollo 16 site. This counter-intuitive result clearly shows that increased illumination (high signal) is a very significant factor in the true resolution of a picture. Next month LRO will pass over all the landing sites at the same altitudes but with the Sun 15° higher above the horizon. By September LRO will be placed in a lower mapping orbit and higher resolution images will be possible.

The LROC NAC image data presented here has not been calibrated, the faint vertical stripes are a normal part of the image, and will be removed later after the full suite of calibration data is collected during the commissioning phase.

LRO’s current elliptical orbit (40 x 199 km), with the low portion of the orbit (perilune) over the south pole, resulted in image scales near the equator ranging from 1.0 meter per pixel (Apollo 16) to 1.4 meter per pixel (Apollo 17).