Archive for September 21st, 2009

Great image of the lunar surface.

Last week the LRO spacecraft lowered its orbit into the 50-km mapping orbit after three months in an elliptical (30 km by 200 km) commissioning orbit. Many engineering tests were performed with the spacecraft and all the instruments during the busy commissioning phase of the mission. The LROC test images were of deep space, stars, nighttime Moon, and vertical views of the lunar surface. Occasionally some extreme oblique views were shuttered as a result of specific test criteria. One measure of a camera’s ability to capture fine detail is the amount of light that is scattered in the optics. In a perfect camera, all light rays enter the aperture and end up in focus in the correct pixel. However, in reality some percentage of light is scattered in the optics, off structures in the telescope, or even reflected off the CCD. If there is no scattering, then no light rays strike pixels looking at space – by measuring the signal level in “space pixels” against those seeing the illuminated surface a good measure of light scattering is easily made. As it turns the scattered light in the NACs is very low (a good thing), about one percent.

An added bonus from this engineering test is the spectacular view across the lunar surface! There are no named lunar features in this image, which is centered in the lunar highlands over 450 km northwest of Mare Humboltianum at approximately 65.5°N, 55.6°E. The regions which appears dark, flat, and level in the distance are not mare basalts as you might expect, but are light plains emplaced as ejecta by large basin-forming impacts.

Credit: NASA/GSFC/Arizona State University

video of the SCA NASA911 with Discovery atop landing at KSC in case you missed it. Along with a picture.

ESA astronaut Frank De Winne does a demonstration on how you measure mass in a weightless environment.

Discovery spent the night at Barksdale AFB in Louisiana, and departed early this morning for Kennedy Space Center. Pictures below are from yesterday morning as Discovery left Edwards AFB.

Again, you can track the progress here.

The 747 Shuttle Carrier Aircraft with shuttle Discovery on top has departed Barksdale Air Force Base in Shreveport, Louisiana and is now heading toward Kennedy Space Center. The aircraft took off from Barksdale at about 9:40 a.m. EDT.
Without any weather delays it is about a two-hour, 45-minute flight to Kennedy. The earliest Discovery would arrive at Kennedy’s Shuttle Landing Facility is about 12:30 p.m. But the team is going to have to fly around a line of showers over central Louisiana first and then see whether storms currently around Kennedy will permit a landing. If weather is not cooperative, Discovery could divert to MacDill Air Force Base in Tampa, Fla.

Another picture taken from the International Space Station by the Expedition 20 crew.

The 38-kilometer-long (about 24 miles) Lago do Erepecu (Lake Erepecu) in Brazil runs parallel to the lower Rio Trombetas (Trombetas River), which snakes along the lower half of this astronaut photograph. Waterbodies in the Amazon rainforest are often so dark they can be difficult to distinguish. In this image, however, the lake and river stand out from the uniform green of the forest in great detail as a result of sunglint on the water surface. Sunglint is the mirror-like reflection of sunlight off of a surface directly back towards the viewer, in this case an astronaut onboard the International Space Station.

Forest soil is red, as shown by airfield clearings near Porto Trombetas (image far lower right), a river port on the south side of the Trombetas River. The Trombetas flows into the Amazon River from the north about 800 kilometers (497 miles) from the Amazon mouth. Despite being so far from the sea, seagoing ore ships export most of Brazil’s bauxite from Porto Trombetas. Bauxite is the raw material used to produce aluminum. (The Trombetas bauxite mine is beyond the lower edge of the image).

Central Amazonia has many lakes like Erepecu—relatively straight, large waterbodies located just off the main axis of the large rivers. These lakes began as rivers that carved deeply into the landscape during periods of low sea level accompanying ice ages in the past 1.7 million years. When sea level was low, the gradient from a river’s headwaters to its end at the ocean was steeper, and rivers flowed faster and carved deeper beds. During intervening warm periods, rising sea level reduced the gradient at the river’s end so much that it faced an impossible task—flowing uphill to the ocean.

The only way a river could have continued to flow to the sea is if it was carrying enough sediment to fill the deep river valleys carved during low sea level, creating a new “ground level” for the river to flow across. Many larger rivers like the Trombetas and the Amazon itself carried enough loose sediment to fill their deeply carved valleys, and then to trace sinuous courses (lower part of image) across the new beds. But smaller rivers that carried less sediment could not fill in their deep valleys; instead, the valleys acted like troughs. The river water poured in, but couldn’t flow out because of rising sea level, so lakes like Erepecu formed.

Caption by M. Justin Wilkinson.

Video from the Charged Aerosol Release Experiment (CARE) launch that happened on the 19th.