{{Italic disambiguation}} thumb|The gravity science experiment for ''Juno'' involves using communication hardware on ''Juno'' and Earth. Deep Space Network antenna shown here. thumb|The ''Juno'' gravity experiment makes use of spacecraft's antenna, which are used to send radio signals to Earth with precise timing. This allows the Doppler effect to be recorded, which in turn allows the calculation of the gravity field around Jupiter. thumb|Jupiter shown in the image 'Jupiter Marble' as recorded by ''Juno'' The '''Gravity Science''' experiment and instrument set aboard the ''Juno'' Jupiter orbiter is designed to monitor Jupiter's gravity.<ref name="Instrument Overview – Juno">{{Cite web|url=http://spaceflight101.com/juno/instrument-overview/|title=Instrument Overview – Juno|website=spaceflight101.com|access-date=2017-01-05}}</ref><ref>{{Cite news|url=http://www.space.com/33053-nasa-juno-spacecraft-jupiter-gravity.html|title=Jupiter's Gravity Embraces NASA's Juno Spacecraft|newspaper=Space.com|access-date=2017-01-05}}</ref><ref name="missionjuno.swri.edu">{{Cite web|url=https://www.missionjuno.swri.edu/media-gallery/instruments|title=Juno's Instruments {{!}} Mission Juno|website=Mission Juno|access-date=2017-01-05}}</ref> It maps Jupiter's gravitational field, which will allow the interior of Jupiter to be better understood.<ref name="missionjuno.swri.edu"/> It uses special hardware on ''Juno'', and also on Earth,<ref name="Instrument Overview – Juno"/> including the high-gain K-band and X-band communication systems of the Deep Space Network as well as ''Juno''{{'}}s Ka-band Translator System (KaTS).<ref name="Instrument Overview – Juno"/><ref name="europlanet-eu.org">{{Cite web|url=http://www.europlanet-eu.org/juno-europe/|title=European Involvement in Juno {{!}} Europlanet Outreach|website=www.europlanet-eu.org|access-date=2017-01-05}}</ref> These components work together to detect minute changes in radio frequency (Doppler shift) to measure the spacecraft's velocity over time.<ref>{{Cite web | url=http://spaceflight101.com/juno/instrument-overview/ |title = Instrument Overview – Juno}}</ref> The KaTS box was funded by the Italian Space Agency and overseen by professor Luciano Iess from University La Sapienza in Rome.<ref name="europlanet-eu.org"/> KaTS detects signals coming from the DSN on Earth, and then sends replies in a very precise way that allows the velocity of ''Juno'' to be determined to within 0.001 millimeters per second.<ref name="europlanet-eu.org"/> The spacecraft receives a tone signal on the X or Ka band and then replies using the Ka-band radio.<ref name="Instrument Overview – Juno"/>
As the spacecraft traverses the space near Jupiter, the planet, and even variations in the planets interior, cause a variation in ''Juno'' velocity.<ref name="sciencefocus.com">{{Cite news|url=http://www.sciencefocus.com/article/space/what-will-we-learn-juno-mission|title=What will we learn from the Juno mission?|newspaper=Science Focus|access-date=2017-01-05}}</ref> The '''gravity science''' experiment measures these velocity changes using a combination of hardware on Earth and the spacecraft, which allows the effect of gravity to be measured, and thereby mass variations in Jupiter's interior.<ref name="sciencefocus.com"/>
Communication signals:<ref name="europlanet-eu.org"/><ref name="Instrument Overview – Juno"/> *Deep Space Network sends a tone signal at 7.1 GHz (X-band) and 34 GHz (Ka-Band) *''Juno'' KaTS sends tone signal at 8.5 GHz (X-band) and 32 GHz (Ka-Band)
''Juno'' launched in 2011 and arrived at Jupiter orbit in July 2016.<ref name="nasa.gov">{{Cite news|url=https://www.nasa.gov/mission_pages/juno/spacecraft/index.html|title=Juno Spacecraft and Instruments|last=Greicius|first=Tony|date=2015-03-13|newspaper=NASA|access-date=2017-01-04|archive-date=2017-05-09|archive-url=https://web.archive.org/web/20170509053559/https://www.nasa.gov/mission_pages/juno/spacecraft/index.html|url-status=dead}}</ref>
The GS was planned out to be used on orbits 4, orbit 9, and orbits 10 through 32.<ref name="Gravity Science Orbits">{{Cite web|url=https://www.missionjuno.swri.edu/orbit?show=hs_orbit_story_gravity-science-orbits|title=Gravity Science Orbits|website=Mission Juno|access-date=2017-02-07}}</ref> When GS operates it must point its antenna at Earth, and is not operated simultaneously with the Microwave Radiometer instrument on ''Juno''.<ref name="Gravity Science Orbits"/> The parameters of the GS experiment were adjusted to account for a 53-day orbit the Juno spacecraft ended up being in.<ref name=":0">{{Cite book|last1=Buccino|first1=D.|last2=Kahan|first2=D.|last3=Yang|first3=O.|last4=Oudrhiri|first4=K.|title=2018 IEEE Aerospace Conference |chapter=Initial operations experience and results from the Juno gravity experiment |date=March 2018|pages=1–8|doi=10.1109/AERO.2018.8396438|isbn=978-1-5386-2014-4|s2cid=49540278 }}</ref>
The GS experiment uses Deep Space Network's DSS-25 antenna which is equipped with simultaneous dual X- and Ka-band transmitters and receivers, as well as the spacecraft which also has X and Ka-band radio systems.<ref name=":0" />
== Observations == The 53-day orbit (rather than the originally planned orbit) produced certain challenges for the GS experiment, which required signals to be sent between the DSN on Earth and the spacecraft.<ref name=":0" /> It was possible to make measurements, although various configurations were tried for the first five Perijoves between July 2016 and September 2017.<ref name=":0" />
It was possible to use the data from the observations, and from just the first two Perijoves the accuracy of Jupiter's gravity field record was increased by factor of five according to one report.<ref name=":0" /> This data allowed further insight to Jupiter's internal structure.<ref name=":0" />
Additional data collections refined by understanding of the early recordings is planned for the experiment.<ref name=":0" />
==See also== *NASA Deep Space Network *GRACE and GRACE-FO (GRACE, gravity science spacecraft for Earth) *Jovian Infrared Auroral Mapper (ASI contributed instrument) *REX (''New Horizons'') (Radio science experiment for Pluto probe)
==References== {{reflist}}
==External links== *[https://www.nasa.gov/mission_pages/juno/spacecraft/index.html NASA – ''Juno'' instruments] {{Webarchive|url=https://web.archive.org/web/20170509053559/https://www.nasa.gov/mission_pages/juno/spacecraft/index.html |date=2017-05-09 }} *[https://web.archive.org/web/20190927141544/https://catalog.data.gov/dataset/juno-jupiter-raw-gravity-science-1-v1-0 JUNO JUPITER RAW GRAVITY SCIENCE 1 V1.0] <ref>https://ieeexplore.ieee.org/document/9843752</ref> {{Juno spacecraft}}
Category:Juno (spacecraft) Category:Spacecraft instruments Category:Italian Space Agency