(From west to east)

• Irene is in the constellation of Virgo.
• Iris is in the constellation of Sagittarius.
• Juno is in the constellation of Pisces.
• Vesta is in conjunction with the Sun on the 22nd.
• Information about the Minor Planets can be found at the Minor Planet Observer website.

"A bright arc within Saturn's faint G ring holds a tiny gift.

A small moonlet is just visible as a short streak near the ansa of the G ring arc in the top of two versions of the same image. The second (bottom) version of the image has been brightened to enhance the visibility of the G ring. The other streaks in this version of the image are stars smeared by the camera's long exposure time of 26 seconds. This version of the image shows a gap in the G ring which was faintly visible in an earlier Cassini movie (see Rounding the Corner).

The moonlet, dubbed S/2008 S 1 (and recently named Aegaeon), is likely a major source of the material of the G ring (see Tiny Moonlet Within G Ring Arc).

This view looks toward the sunlit side of the rings from about 1 degrees below the ring plane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Jan. 28, 2009. The view was acquired at a distance of approximately 1.2 million kilometers (746,000 miles) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 27 degrees. Image scale is 7 kilometers (4 miles) per pixel."

Cassini Imaging Team

"Things are going well out in the cold space between Saturn and Uranus where New Horizons is now. We're deep in planning for our spacecraft's annual checkout this summer, which begins on July 7. But that's not what I want to write about today: instead, it's something called EPDR.

Despite still being more than six years and just over 18 astronomical units from the Pluto system, the New Horizons project team is conducting the second and final portion of our Pluto Encounter Preliminary Design Review (EPDR) today and tomorrow (May 20-21) at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md.

We conducted the first portion of the EPDR on January 7-8. EPDR part two is another two-day confab, in which the New Horizons technical and management teams will present the detailed, minute-by-minute timeline of our planned 2015 Pluto encounter to a review team of expert planetary planners from across the nation. EPDR represents the culmination of almost two years of intense encounter planning involving the entire New Horizons science and mission team, and the stakes are high Ñ this is the main technical review of what will take place when we conduct the first exploration of Pluto and its satellites."

New Horizons gallery

Mission Status Report: NASA's Dawn Mission

"With Mars disappearing in its metaphorical rearview mirror, NASA's Dawn spacecraft's next stop is the asteroid belt and the giant asteroid Vesta. Dawn got as close as 549 kilometers (341 miles) to the Red Planet during its Tuesday, Feb. 17, flyby.

Dawn's navigators placed the spacecraft on a close approach trajectory with Mars so the planet's gravitational influence would provide a kick to the spacecraft's velocity. If Dawn had to perform these orbital adjustments on its own, with no Mars gravitational deflection, the spacecraft would have had to fire up its engines and change velocity by more than 9,330 kilometers per hour (5,800 miles per hour).

The achieved goal of the flyby was to obtain this orbital pick-me-up, making possible its voyage to asteroid Vesta and, later, the dwarf planet Ceres. But Dawn's science teams used this massive target of opportunity to also perform calibrations of some of the scientific instruments. Calibration images were taken by Dawn's framing camera, and the Gamma Ray and Neutron Detector also observed Mars for calibration. These data will be compared to similar observations taken by spacecraft orbiting Mars."

"MESSENGER Co-Investigator Stanton J. Peale, a professor emeritus renowned for his work in planetary science and astrophysics at University of California, Santa Barbara, was among the 72 new members elected to the National Academy of Sciences. The election was held April 28 during the business session of the 146th annual meeting of the Academy. Those elected bring the total number of active members to 2,150, now including four members of the MESSENGER Science Team.

Peale is a leading expert on planetary dynamics. He developed the technique by which MESSENGER will measure the size and state of Mercury's core, and he will lead the interpretation of Mercury Laser Altimeter (MLA) measurements of Mercury's rotation and physical libration.

His theory for Mercury's forced libration, equivalent to small variations in Mercury's spin rate, was recently utilized to interpret Earth-based radar measurements of Mercury's motions. Those observations can be explained only if Mercury's core is at least partially molten, a finding that has helped scientists better understand Mercury's thermal history and the generation of the planetÕs intrinsic magnetic field."

"PASADENA, Calif. -- Heading into a period of the Martian year prone to major dust storms, the team operating NASA's twin Mars rovers is taking advantage of eye-in-the-sky weather reports.

On April 21, Mars will be at the closest point to the sun in the planet's 23-month, elliptical orbit. One month later, the planet's equinox will mark the start of summer in Mars' southern hemisphere. This atmospheric-warming combination makes the coming weeks the most likely time of the Martian year for dust storms severe enough to minimize activities of the rovers."

"A simulated fly-through using the newly assembled imagery is available online.

The fly-through plus tools for wandering across and zooming into the large image are at THEMIS."

Daily Mars Odyssey THEMIS Images
Can be found at the Thermal Emission Imaging System (THEMIS) website.

The Odyssey data are available through a new online access system established by the Planetary Data System.

SPIRIT UPDATE: Recovery Efforts Continue - sols 1913-1919, May 21-27, 2009:

"Spirit remains stationary, pending development of a recovery strategy to free her from the loose, soft terrain on the west side of Home Plate.

The rover continues to conduct extensive remote sensing observations of its local terrain. A 360-degree color panorama, called the Calypso panorama, is being collected, and includes the rover's deck. Additional mini-thermal emission spectrometer (TES) observations have been sequenced. Thanks to the extra energy made possible by recent solar array dust cleaning events, Spirit has been collecting measurements of atmospheric argon almost every day using its alpha-particle X-ray spectrometer (APXS).

The project continues to investigate the left middle wheel stall that occurred back on Sol 1899 (May 6, 2009). A small (4-degree) backward wheel motion test was sequenced on Sol 1913 (May 21, 2009). The wheel and motor performed satisfactorily. A second, larger test (16 degrees) was performed on Sol 1916 (May 24, 2009), and again, the wheel performed satisfactorily, showing no signs of a jam in the backward direction.

Pending the recertification of the robotic arm (the instrument deployment device, or IDD), a microscopic imager (MI) mosaic of Spirit's underbelly is planned for this coming weekend to assess the rover's embedded condition.

On the ground, testing with the surface system testbed (SSTB) rover at JPL is held up due to a computer server disk crash. That server is being restored from a huge backup tape, which is taking considerable time. In parallel, the SSTB-Lite rover (an alternate, lower-fidelity testbed rover) is being set up to conduct early tests of candidate soil simulants.

Spirit is very active, with abundant energy. Once again, Spirit has received a beneficial solar array dust cleaning. Dust factor (a measure of array cleanliness) improved about 10 percent on Sol 1918 (May 26, 2009). As of Sol 1919 (May 27, 2009), solar array energy production was 843 watt-hours, enough to run a 100-watt bulb for more than eight hours, with atmospheric opacity (tau) around 0.606. The dust factor increased to 0.774, meaning that about 77.4 percent of the sunlight hitting the solar array penetrates through the dust on the array.

Spirit's total odometry as of Sol 1919 (May 27, 2009) is 7,729.93 meters (4.8 miles)."

OPPORTUNITY UPDATE: Passing The 10-Mile Mark - sols 1893-1899, May 21-28, 2009:

"Opportunity is driving again, making good progress toward the distant Endeavour crater.

On Sol 1893 (May 21, 2009), Opportunity drove about 77 meters (252.6 feet) to the south. Motor currents in the right front wheel are elevated. After a few sols rest to collect atmospheric argon measurements with the alpha-particle X-ray spectrometer (APXS) and targeted Pancam observations, the rover drove about another 54 meters (177.2 feet). The right front wheel continued to show elevated current levels, but the levels are not increasing.

With its drive on Sol 1897 (May 25, 2009), Opportunity achieved another milestone, with its odometer surpassing the 10-mile mark (more than 16,093 meters)! Another drive on the next sol added another 50 meters (164 feet).

On Sol 1899 (May 28, 2009), the rover used its robotic arm (instrument deployment device, or IDD) to collect some sky flats (images of the sky) using its microscopic imager (MI). The sky images will be used for calibration purposes.

As of Sol 1899 (May 28, 2009), Opportunity's solar array energy production was 436 watt-hours, the atmospheric opacity (tau) remained around 0.651, and the dust factor was 0.564.

Opportunity's total odometry as of Sol 1899 (May 28, 2009) is 16,184.19 meters (10.06 miles)."

Landing sites

"Camera-team members are now posting tens of thousands of new image products each month from the high-resolution camera on NASA's Mars Reconnaissance Orbiter."

MARS RECONNAISSANCE ORBITER HIRISE IMAGES
All of the HiRISE images are archived here.