Thursday, May 23, 2013
May 22 update: Mission controllers received confirmation from the spacecraft today that its MWR, JEDI and Waves instruments were powered off as planned. The magnetometer experiment remains powered on at low data rates. The planned instrument shutdown was done in preparation for the spacecraft’s upcoming switch to its lower data rate antennas as it begins the next phase of its mission, dubbed “Inner Cruise 3” on May 29.
The solar-powered Juno spacecraft and its saucer-shaped high-gain antenna (or HGA) always point sunward, but while Juno is in the inner solar system, Earth’s position on the sky shifts dramatically. Earth’s movement means that Juno cannot always use its HGA and benefit from its high data rate connection. For this reason, the spacecraft has a suite of antennas that allow communications with Earth from other angles, but at the cost of lower data rates, resulting in a reduction in Juno’s ability to transmit science data during that time. Juno’s science instruments will be powered on again shortly before the Earth flyby, slated for Oct. 9.
May 10 update: The Juno spacecraft is in excellent health and is operating nominally. As of May 10, Juno was approximately 50 million miles (80 million kilometers) from Earth. The one-way radio signal travel time between Earth and Juno is currently about 4.5 minutes. Juno is currently traveling at a velocity of about 16 miles (25 kilometers) per second relative to the sun, and increasing. Velocity relative to Earth is about 4.7 miles (7.6 kilometers) per second. Juno has now traveled 722 million miles (1.2 billion kilometers) since launch.
Other recent spacecraft significant events
Juno’s mission ops team performed a flush of the spacecraft’s main engine on May 1, firing the engine for a couple of seconds. The team does this maintenance activity about once per year to flush contaminants from the propellant lines that feed the main engine.
Available power to Juno’s solar arrays continues to increase as the spacecraft heads closer to the sun on approach to its Earth flyby gravity assist maneuver on Oct. 9. Juno is now approximately 1.45 AU from the sun (i.e., inside the orbit of Mars), after having reached a maximum distance from the sun of 210 million miles (338 million kilometers, or 2.3 AU) in Sept. 2012. The spacecraft reaches perihelion, the closest point to the sun in its orbit, in August 2013. An AU, or astronomical unit, is a convenient measure of distance between places in the solar system. It is equal to the distance from the Sun to Earth (93 million miles or 150 million kilometers).