• For Moratorium on Sending Commands to Mars, Blame the Sun

    From baalke@1:2320/100 to sci.space.news on Thu Aug 24 23:35:06 2017
    From Newsgroup: sci.space.news


    https://www.jpl.nasa.gov/news/news.php?feature=6895

    For Moratorium on Sending Commands to Mars, Blame the Sun
    Jet Propulsion Laboratory
    July 14, 2017

    This month, movements of the planets will put Mars almost directly behind
    the sun, from Earth's perspective, causing curtailed communications between Earth and Mars.

    NASA will refrain from sending commands to America's three Mars orbiters
    and two Mars rovers during the period from July 22 to Aug. 1.

    "Out of caution, we won't talk to our Mars assets during that period because we expect significant degradation in the communication link, and we don't
    want to take a chance that one of our spacecraft would act on a corrupted command," said Chad Edwards, manager of the Mars Relay Network Office
    at NASA's Jet Propulsion Laboratory, Pasadena, California.

    Data will keep coming from Mars to Earth, although loss or corruption
    of some bits is anticipated and the data will be retransmitted later.
    "We will continue to receive telemetry, so we will have information every
    day about the status of the vehicles," Edwards said.

    As seen from Earth, Mars periodically passes near the sun about every
    26 months, an arrangement called "Mars solar conjunction." During most
    solar conjunctions, including this year's, Mars does not go directly behind the sun.

    Viewers using proper eye protection to watch the total solar eclipse on
    Aug. 21 will gain a visible lesson in why Mars doesn't need to be directly behind the sun for communications between Earth and Mars to be degraded.
    The sun's corona, which always extends far from the surface of the sun, becomes visible during total eclipses. It consists of hot, ionized gas,
    which can interfere with radio waves that pass through it.

    To prevent the possibility of the ionized gas near the sun corrupting
    a command radioed to a spacecraft at Mars, NASA avoids transmitting for
    a period including several days before and after Mars gets closest to
    passing behind the sun.

    Teams that operate Mars orbiters and rovers have been preparing for weeks
    in anticipation of the moratorium that will begin on July 22.

    "The vehicles will stay active, carrying out commands sent in advance,"
    said Mars Program Chief Engineer Hoppy Price, of JPL. "Orbiters will be
    making their science observations and transmitting data. The rovers won't
    be driving, but observations and measurements will continue."

    The rover teams are determining the most useful sites for the rovers Curiosity and Opportunity to remain productive during the solar-conjunction period.

    All of NASA's active Mars missions have experience from at least one previous solar conjunction. This will be the eighth solar conjunction period for
    the Mars Odyssey orbiter, the seventh for the Opportunity rover, the sixth
    for the Mars Reconnaissance Orbiter, the third for the Curiosity rover
    and the second for the MAVEN orbiter.

    Edwards said, "All of these spacecraft are now veterans of conjunction.
    We know what to expect."

    A video showing Mars solar conjunction geometry is at:

    http://mars.nasa.gov/allaboutmars/nightsky/solar-conjunction

    NASA's five current Mars missions, plus Mars missions scheduled for launches in 2018 and 2020, are part of ambitious robotic exploration to understand Mars, helping to lead the way for sending humans to Mars in the 2030s.

    NASA's Goddard Space Flight Center manages the MAVEN project for the principal investigator at the University of Colorado, Boulder, and for the NASA
    Science Mission Directorate, Washington. JPL, a division of Caltech in Pasadena, manages the Odyssey, Opportunity, Reconnaissance Orbiter, and Curiosity projects, and NASA's Mars Exploration Program, for the Science Mission Directorate. Lockheed Martin Space Systems, Denver, built all
    three NASA Mars orbiters. For more about NASA's Mars Exploration Program, visit:

    https://mars.jpl.nasa.gov

    https://www.nasa.gov/mars

    News Media Contact
    Guy Webster
    Jet Propulsion Laboratory, Pasadena, Calif.
    818-354-6278
    guy.webster@jpl.nasa.gov

    Laurie Cantillo / Dwayne Brown
    NASA Headquarters, Washington
    202-358-1077 / 202-358-1726
    laura.l.cantillo@nasa.gov / dwayne.c.brown@nasa.gov

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