"conjunction or opposition of a heavenly body with the sun," 1650s, from L.L. syzygia, from Gk. syzygia "yoke, pair, union of two, conjunction," from syzygein "to yoke together," from syn- "together" + zygon "yoke" - Online Etymology Dictionary
Astronomy and Space Exploration have many interesting connections. Recent news stories about them which caught my attention are just over the Event Horizon squiggle.
Join me below the squiggle. ⤵
Several stories about the Moon have been in the news this week. They have some interesting connections to present and past events.
GRAIL is Heading for the Moon
The GRAIL mission will place two spacecraft into the same orbit around the Moon. As they fly over areas of greater and lesser gravity, caused both by visible features such as mountains and craters and by masses hidden beneath the lunar surface, they will move slightly toward and away from each other. An instrument aboard each spacecraft will measure the changes in their relative velocity very precisely, and scientists will translate this information into a high-resolution map of the Moon's gravitational field.
GRAIL stands for Gravity Recovery and Interior Laboratory. GRAIL-B and GRAIL-A are scheduled to be launched together September 10 at 8:29:45 a.m. EDT. There is a second launch window at 9:08:52 a.m. EDT. They will coast on similar, but different trajectories, for 3-4 months before reaching lunar orbit. Once in orbit, they will take 2 more months to refine their orbits.
One spacecraft will follow the other in the same low-altitude, near-circular, near-polar orbit, and they begin formation-flying. The next 82 days will constitute the science phase, during which the spacecraft will map the Moon's gravitational field.
The science payload on each spacecraft is the Lunar Gravity Ranging System, which will measure changes in the distance between the two spacecraft down to a few microns -- about the diameter of a red blood cell. Each spacecraft will also carry a set of cameras for MoonKAM, marking the first time a NASA planetary mission has carried instruments expressly for an education and public outreach project.
MoonKam is a Sally Ride Science backed project. GRAIL MoonKAM will use dedicated cameras on the two satellites to engage middle schools across the country in lunar exploration. Students in grades 5-8 will select targets and send requests to the GRAIL MoonKAM Mission Operations Center (MOC). Students will use the images to study the lunar features.
Apollo - Footprints on the Moon
The images can be found
here at the Lunar Reconnaissance Orbiter (LRO) web site. In each image of the landing site, there is a vertical line in the middle.
Drag the vertical line left and right to reveal the more detailed scene.
LRO - North Pole of the Moon
Click on the image for an enlarged view. The Moon's north polar region was assembled from images taken by the Lunar Reconnaissance Orbiter Camera, or LROC. An objective of LROC is to identify regions of permanent shadow and near-permanent illumination. LROC has acquired thousands of Wide Angle Camera images approaching the north pole in its polar orbit. From 983 images, scientists produced this mosaic, taken over a one month period during northern summer. It shows the pole when it is best illuminated. Regions that are in shadow during this northern summer are likely to be in permanent shadow.
Perhaps you recall the LCROSS mission last year. In that mission, a spent rocket stage was directed to impact a crater in the south polar region of the Moon. A following spacecraft monitored the plume as it, too, descended and impacted near the rocket stage. Lunar Reconnaissance Orbiter (LRO) and Lunar CRater Observation and Sensing Satellite (LCROSS) were launched at the same time on June 18, 2009.
The mission found evidence that the lunar soil within shadowy craters is rich in useful materials, and the moon is chemically active and has a water cycle. Scientists also confirmed the water was in the form of mostly pure ice crystals in some places. The results are featured in six papers published in the Oct. 22 issue of Science.
"NASA has convincingly confirmed the presence of water ice and characterized its patchy distribution in permanently shadowed regions of the moon," said Michael Wargo, chief lunar scientist at NASA Headquarters in Washington. "This major undertaking is the one of many steps NASA has taken to better understand our solar system, its resources, and its origin, evolution, and future."
The twin impacts of LCROSS and a companion rocket stage in the moon's Cabeus crater on Oct. 9, 2009, lifted a plume of material that might not have seen direct sunlight for billions of years. As the plume traveled nearly 10 miles above the rim of Cabeus, instruments aboard LCROSS and LRO made observations of the crater and debris and vapor clouds. After the impacts, grains of mostly pure water ice were lofted into the sunlight in the vacuum of space.
I think this was an interesting syzygy of stories this time. NASA has been getting a great deal of information from its space exploration craft. Let's hope the GRAIL A and B craft will prove equally successful.
Thanks for joining me...jim