Examples... Crater Resolution...


Apollo 11 Area Resolution Examples


Description

The area around the location of the first human landing on the Moon (the Apollo 11 Site) is a popular, but difficult, target for amateur lunar imagers.

Measured Craterlet Diameters

The diameters of 235 representative craterlets were measured using the LTVT Circle Drawing Tool on the USGS high-resolution scans of Lunar Orbiter V medium resolution frames LO-V-075M and LO-V-076M . LTVT calibration data for these images is available on the Lunar Orbiter page. Diameters were measured using zooms of 500 to 1000 giving ~0.03 km precision. The areas around Armstrong, and even more so Collins, were studied more intensively than the rest of the image.

The data, presented as an LTVT dot file with the measured craterlets listed and numbered in order of descending size, can be downloaded here:
(8 kb; rev. 31 Jul 2008)


This overview image gives the diameters (in kilometers) of those 1.0 km and up, and indicates (by unlabeled dots) the positions of many others that were found to be smaller than than 1.0 km. Collins and Armstrong are the two largest craters at the top, and Moltke is the large one near the bottom. Like all subsequent images, this somewhat oblique view from lunar orbit has been remapped to a zero libration Earth-based view.

external image normal_Apollo_11_area_craterlets_LO-V-075M.JPG click for full-sized image

The following detail shows the area around and to the southwest of Collins (the area in the upper left of the previous image). The positions of all measured craters (some as small as 0.4 km) are indicated by dots. Craterlets in the range 0.80-1.00 km are indicated in green, and those 1.00 km and up in red. In addition, those with diameters of 0.60 km and up are labeled. The diameters of the unlabeled craterlets can be found in the dot file.

external image normal_Collins_area_craterlets_LO-V-075M.JPG click for full-sized image

The actual Apollo 11 landing site is near the bottom of the detailed field, a little to the left of center. See the LPI presentation or Dan Durda's nicely arranged Exploring the Apollo Landing Sites zoom-in sequences (click on "Apollo 11") for orientation.

Earth-based Images


Comparison of Earth-based photos with the preceding reference images is helpful for verifying claims of sub-kilometer crater detection. For example, here are cropped samples from two very good amateur images showing exactly the same area as the Lunar Orbiter detail:

Sample
Imager
Aperture [mm]
Wavelength
Moon Diam [arc-sec]
Min Crater [km]
Corrected [km]
external image Collins_area_craterlets_Lammel.JPG
Stefan Lammel
254
green
1953
1.1
1.1
external image Collins_area_craterlets_Daversin.JPG
Bruno Daversin
600
?
1839
0.7
0.7

Right-click on the thumbnails to open the full-sized screenshots in separate windows or browser tabs for comparison with the Lunar Orbiter detail.

The LPOD in which the second image appeared suggested it was detecting craterlets as small as 0.4 km diameter immediately to the west of Collins. This seems to have been a bit optimistic. The most prominent craterlets to the left of Collins range in size from 0.7-0.9 km in diameter, and some of the apparent detail shown at this level in the Earth-based image is spurious.




This page has been edited 5 times. The last modification was made by - JimMosher JimMosher on Jun 5, 2009 7:25 pm