Tuesday, September 6, 2011

LRO Briefing: Latest close-ups of Apollo sites

Figure 1: Resolution comparison between nominal orbit images of the Apollo 17 landing site (a, b) and the new low orbit image (c; 27 cm x 56 cm pixel size - View the full size image released by NASA, September 6, HERE). What is visible in an image is not simply a matter of the size of a pixel projected onto the surface. Sun angle and direction are also important factors, as is the exposure level. When the Sun is high above the horizon differences in surface brightness are enhanced, and when the Sun is low surface roughness is more obvious. Linear features are enhanced when they lie perpendicular to the direction to the Sun, and tend to disappear when parallel. When an image is underexposed or overexposed contrast and detail suffer. The top two images (a,b) have larger pixel scales (49 cm, 54 cm) and incidence angles (55° and 21° from vertical) that bracket the new higher resolution image (c; 45°) [NASA/GSFC/Arizona State University].
NASA HQ - Sept. 6, 2011 - According to Mark Robinson, principle investigator for the Lunar Reconnaissance Orbiter Camera (LROC) at Arizona State University at Tempe, his team's scientific goals during August's lower perilune passes over the Moon by LRO involved the LROC's Wide Angle Camera (WAC). Nevertheless, using vehicle slews as high as 20 degrees off nadir allowed for unprecedented close-up examination of three of the six Apollo surface expedition sites using LROC's Narrow Angle Cameras (NAC).

Since arriving in lunar orbit in 2009 the left and right LROC has surveyed 30 percent of the lunar surface at an average resolution of 50 cm per pixel. In the month-long lower altitude skims the LROC NAC system was able to sweep up views of the landing sites of Apollo 12 in Oceanus Procellarum, relatively nearby Apollo 14, south of Copernicus crater, and Apollo 17 in Taurus Littrow valley on the southeastern side of Mare Serenitatis, from as law as 22 kilometers.

In its polar orbit this close skim over these three landing sites allowed for an east-west, or "cross track" improvement in resolution to 25 centimeters per pixel. At an orbital velocity of 1640 meters per second, however, the north-south, or "down track" resolution required some image correction.

The tracks made in 1969 by astronauts Pete Conrad and Alan Bean, the third and fourth humans to walk on the moon, can be seen in this LRO image of the Apollo 12 site. The location of the descent stage for Apollo 12's lunar module, Intrepid, also can be seen. See the full-sized image released by NASA HERE.

Conrad and Bean performed two moon walks on this flat lava plain in the Oceanus Procellarum region of the moon. In the first walk, they collected samples and chose the location for the lunar monitoring equipment known as the Apollo Lunar Surface Experiments Package (ALSEP). The ALSEP sent scientific data about the moon's interior and surface environment back to Earth for more than seven years.

One of the details visible in this image is a bright L-shape that marks the locations of cables running from ALSEP's central station to two of its instruments. These instruments are probably (left) the Suprathermal Ion Detector Experiment, or SIDE, which studied positively charged particles near the moon's surface, and (right) the Lunar Surface Magnetometer, or LSM, which looked for variations in the moon's magnetic field over time; these two instruments had the longest cables running from the central station. Though the cables are much too small to be seen directly, they show up because the material they are made from reflects light very well.

In the second moon walk, Conrad and Bean set out from the descent stage and looped around Head crater, visiting Bench crater and Sharp crater, then headed east and north to the landing site of Surveyor 3. There, the astronauts collected some hardware from the unmanned Surveyor spacecraft, which had landed two years earlier.

The two astronauts covered this entire area on foot, carrying all of their tools and equipment and more than 32 kilograms (roughly 60 pounds) of lunar samples.

The paths left by astronauts Alan Shepard and Edgar Mitchell on both Apollo 14 moon walks are visible in this LRO image. (At the end of the second moon walk, Shepard famously hit two golf balls.) The descent stage of the lunar module Antares is also visible.

Apollo 14 landed near Fra Mauro crater in February 1971. On the first moon walk, the astronauts set up the lunar monitoring equipment known as the Apollo Lunar Surface Experiments Package (ALSEP) to the west of the landing site and collected just over 42 kilograms (about 92 pounds) of lunar samples. Luckily for them, they had a rickshaw-style cart called the modular equipment transporter, or MET, that they could use to carry equipment and samples. View the full-size image released by NASA HERE [NASA/GSFC/Arizona State University].

LRO Media Briefing (News Conference, September 6, 2011).

No comments: