Observatories and Instruments

Close-up View of 'Snowman' Craters, Vesta. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Although the mission website is written in the future tense, NASA’s spacecraft Dawn is operating in the present tense. As of August 11, Dawn has been actively studying the asteroid Vesta in an attempt to clarify the creative processes of our early solar system. As the photo above shows, Vesta is a dry asteroid with a basaltic surface formed approximately 4.5 billion years ago. The surface has remained mostly intact ever since (that is, there is not sign of later extrusions of lava from the interior of the asteroid), although it does seem to be significantly cratered in certain sectors. In surveying the asteroid and comparing the results to other objects with origins in the early solar system, NASA hopes to determine the “evolutionary path” objects have followed during their (very long) lives.

Using three different instruments, (a visible Framing Camera, a Visible and Infrared Mapping Spectrometer, and a Gamma Ray and Neutron Spectrometer), Dawn is attempting to capture data that will reveal both the external and the internal characteristics of Vesta. The framing camera is providing images of object in the visible range of the spectrum. The Visible and Infrared Mapping Spectrometer is taking measurements for comparison with laboratory samples to determine Vesta’s mineral composition. The Gamma Ray and Neutron Spectrometer is measuring the energy from gamma rays and neutrons emitted by or bounced off the asteroid. With these measurements, the research team will be able to determine the elemental composition of the asteroid as deep as three feet below the surface.

After Dawn finishes it survey of Vesta, it will move on to study of the dwarf planet Ceres. Ceres is quite different from Vesta—it has a “primitive surface” containing water-bearing minerals and appears to be similar to several of the icy moons of the outer planets of the solar system. It’s possible it may have a weak atmosphere. We’ll know soon (relatively speaking). Dawn is scheduled to depart Vesta in July 2012 and arrive at Ceres in February 2015. Once the Ceres survey is completed, NASA should be able to make an informed comparison of the paths different objects followed during the early years of our solar system.

Dawn baseline interplanetary trajectory for primary mission. Dashed lines represent orbits of Mars, Vesta, and Ceres. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Oxygen in Orion. Image credit: ESA/NASA/JPL-Caltech

Very cool:  the large telescope of the Herschel Space Observatory (formerly called Far Infrared and Sub-millimetre Telescope or FIRST) has detected oxygen molecules in the Orion nebula. The existence of oxygen in space makes sense, since it’s the third most common element in the universe. It’s taken something like 230 years for anyone to detect it, though.

The Herschel Space Observatory is one of those projects that demonstrates the benefits of international collaborative efforts. Herschel is a major mission for the European Space Agency, with several nations contributing to the design and build of the instruments and the spacecraft.* However, Herschel is also supported by NASA resources. NASA’s Herschel Project Office is based at JPL, a major contributor for two of the observatory’s three science instruments. JPL itself is a joint project of sorts, since Caltech manages it for NASA. International, multi-national cooperation at its most productive—they found oxygen, after all.

*By my reckoning, Austria, Belgium, Denmark, Finland, France, Germany, Ireland, Italy, Norway, Netherlands, Portugal, Spain, Sweden, Switzerland, the United Kingdom, and the United States all contributed during the industrial phase of the project.

New findings are in from NEOWISE, the Near Earth Object (NEO, typically a comet or asteroid) observing component of NASA’s Wide-field Infrared Survey Explorer (WISE) telescope.  WISE is/was an infrared surveyor satellite set into polar orbit in 2010. The spacecraft was designed with a limited life span of approximately ten months: one month for testing and checkout, six months for a whole-sky survey, and three months for a second survey meant to identify any changes that had taken place in the sky since the first survey.

April 14, 2011 marked the date of the preliminary release of WISE data. The final release won’t happen for another ten months or so, but we already have some interesting results from released data. Today it was announced that Comet Hartley 2 is leaving a bumpy, pebbly trail behind it with grains as large as golf balls. The last time the comet was surveyed (November 2010, as part of NASA’s EPOXI mission), data showed that the comet was streaming golf ball- to basketball-sized fluffy ice particles. The NEOWISE results indicate that the smaller, golf ball-sized pieces survive farther away from the comet than scientists previously thought, comprising at least part of the comet’s debris trail. According to the NEOWISE team, larger chunks are less likely to be pushed away from the comet’s trail by radiation pressure of the sun. Since these observed particles are in the trail, they must be (relatively) small.

The team was also surprised to note that Hartley 2 is ejecting carbon dioxide gas at a distance of 2.3 AUs from the Sun. Although EPOXI had detected carbon dioxide streaming from comet, it was at a distance considerably closer to the Sun. So, that’s two new things we know about comet behavior today that we didn’t know yesterday. Money well spent.

An abstract of the paper, “WISE/NEOWISE observations of comet 103P/Hartley 2,” which has been accepted by the Astrophysical Journal,  can be read online. If you have access, you download a .pdf of the entire paper.