By Julie Cooper

Each month in “Slice of History” we feature a historical photo from the JPL Archives. See more historical photos and explore the JPL Archives at https://beacon.jpl.nasa.gov/.

Viking Stereo Viewer — Photograph Number 324-1954

This interactive computer-based stereo viewing system was used to analyze Mars topography images generated by the cameras on NASA’s Viking 1 Mars lander. Two 17-inch video monitors faced a scanning stereoscope mounted between them on a table. Left and right lander camera image data were sent to the left and right monitors. Panning controls on the stereoscope helped align one image with the other to create a stereo image, 640 by 512 pixels in size. A mouse was used for finely controlled rotation of the monitors. An article about the system described a prototype mouse, used before this photo was taken in 1976. “The track ball is a baseball-sized sphere protruding from the top of a retaining box and capable of being rotated freely and indefinitely about its center …”

The resulting images could be displayed on additional monitors and were used to create contour maps and other images that aided lander surface operations. The system was developed by Stanford University and NASA’s Jet Propulsion Laboratory in Pasadena, Calif.

This post was written for “Historical Photo of the Month,” a blog by Julie Cooper of JPL’s Library and Archives Group.

By Marc Rayman

NASA’s Dawn spacecraft is less than two months away from getting into orbit around its first target, the giant asteroid Vesta. Each month, Marc Rayman, Dawn’s chief engineer, shares an update on the mission’s progress.

Artist’s concept of the Dawn spacecraft using its ion propulsion system during the approach to Vesta. Image credit: NASA/JPL-Caltech

Dear Dependawnble Readers,

Dawn remains healthy and on course as it continues to approach Vesta. Thrusting with its ion propulsion system, as it has for most of its interplanetary journey so far, the spacecraft is gradually matching its solar orbit to that of the protoplanet just ahead.

As these two residents of the asteroid belt, one very new and one quite ancient, travel around the sun, they draw ever closer. Vesta follows its own familiar path, repeating it over and over, just as Earth and many other solar system bodies do. Dawn has been taking a spiral route, climbing away from the sun atop a blue-green pillar of xenon ions. With an accumulated total in excess of two and a half years of ion thrusting, providing an effective change in velocity of more than 6.5 kilometers per second (14,500 mph), the probe is close to the end of the first leg of its interplanetary trek. On July 16, Vesta’s gravity will capture the ship as it smoothly transitions from spiraling around the sun to spiraling around Vesta, aiming for survey orbit in August. For several reasons, the date for the beginning of the intensive observations there has not yet been set exactly.

Astronomers have estimated Vesta’s mass, principally by measuring how it occasionally perturbs the orbits of some of its neighbors in the asteroid belt and even the orbit of Mars, but this method yields only an approximate value. Because the mass is not well known, there is some uncertainty in the precise time that Dawn will become gravitationally bound to the colossal asteroid. As we have seen before, entry into orbit is quite unlike the highly suspenseful and stressful event of missions that rely on conventional chemical propulsion. Dawn simply will be thrusting, just as it has for 70 percent of its time in space. Orbit entry will be much like a typical day of quiet cruise. That Vesta will take hold at some point will matter only to the many Dawnophiles throughout the cosmos following the mission. The ship will continue to sail along a gently curving arc to survey orbit.

› Continue reading Marc Rayman’s May 27, 2011 Dawn Journal

By Julie Cooper

Each month in “Slice of History” we’ll be featuring a historical photo from the JPL Archives. See more historical photos and explore the JPL Archives at https://beacon.jpl.nasa.gov/.

Ranger Midcourse Motor — Photograph Number 384-5117B

Engineer Ted Metz proudly showed off the Ranger midcourse correction motor in a photo similar to this one that appeared in the May 1965 issue of Lab-Oratory, the JPL employee newsletter. “Since few Lab employees have seen the Ranger and Mariner midcourse propulsion unit, we show here the rocket motor portion of the system held by Propulsion project engineer, Ted Metz. This 50-pound thrust motor utilizes hydrazine fuel and has successfully corrected the trajectories of the Mariner R, Mariner IV and Rangers VI through IX spacecrafts.”

From 1961 to 1965, there were six Ranger flights that failed for various reasons and three very successful ones (Rangers 7, 8, and 9). Mariner R (based on the Ranger spacecraft, also called Mariner 2) had flown by Venus, and Mariner 4 was on the way to Mars.

This post was written for “Historical Photo of the Month,” a blog by Julie Cooper of JPL’s Library and Archives Group.

By Marc Rayman

NASA’s Dawn spacecraft is less than four months away from getting into orbit around its first target, the giant asteroid Vesta. Each month, Marc Rayman, Dawn’s chief engineer, shares an update on the mission’s progress.

Artist’s concept of NASA’s Dawn spacecraft. Image credit: NASA/JPL-Caltech

Dear Conndawnsseurs,

Three and a half years after launch, Dawn continues its travels around the sun, maneuvering to take the same orbital path as Vesta. Following its usual pattern, the spacecraft has spent most of the past month gently thrusting with its ion propulsion system. Some of the thrusting this month, however, was not designed to propel Dawn to Vesta. In addition, mission controllers stopped the thrusting to conduct other planned activities.

Spacecraft that use conventional propulsion coast through space most of the time, just as the moon coasts around Earth, and the planets and asteroids coast around the sun. In contrast, Dawn is in powered flight most of the time, using its ion propulsion system to change its orbit. The flight plan requires pointing the ion thruster in just the right direction to deliver the adventurer to its destination. The spacecraft orientation needed to aim the thruster ends up pointing the main antenna in an arbitrary direction. We have seen before that the robotic craft interrupts thrusting for about eight hours each week to direct the antenna toward Earth for communications.

Ever since Dawn’s trajectory was first being designed, long before launch, it has included coast periods for activities that require orientations incompatible with routine thrusting. One such period was the week of March 14; the previous was in July 2010.

Engineers and scientists operate the science instruments about twice each year to ensure they remain in good condition. This time was the last scheduled use of the sensors prior to their observations of Vesta. All tests showed they are in excellent condition and ready to expose the mysteries of the world they are about to visit.

Controllers transmitted upgraded software to each of the two identical science cameras, containing a few improvements over the version installed in July. The procedure went as smoothly as it had for previous software updates, including the first time such an operation was performed. After each camera received its new software, it performed its standard routine of exercises, just as it did only three weeks after reaching space. The tests confirmed that each camera’s electronics, optics, detector, cover, and filter wheel are in perfect condition.

Sometimes the spacecraft is turned to aim the cameras at carefully selected astronomical targets for their tests; other times, they take pictures of whatever stars happen to be in their field of view. This month’s tests were of the latter type, in which the orientation of the spacecraft was set to keep the antenna pointed at Earth. That put stars from a region near the border between Pisces and Cetus in the grasp of the cameras, quite appropriate for a ship voyaging across the cosmic ocean on its way to a distant and unfamiliar land.

Continue reading this entry from Marc Rayman’s Dawn journal …