[time-nuts] Water on Enceladus - What does this imply about NASA'a ability to measure frequency?
jimlux at earthlink.net
Fri Apr 4 13:50:28 UTC 2014
On 4/4/14 4:30 AM, Bob Camp wrote:
> Back when they were designing this stuff, they were very interested in getting into the parts in 10 to the 15th. They didn’t get there, but that was the desire.
http://lasp.colorado.edu/~horanyi/graduate_seminar/RSS.pdf is a good
presentation with design and performance at a high level. It has plots
of the USO and maser performance, etc.
http://lasp.colorado.edu/~horanyi/graduate_seminar/Radio.pdf is a good
paper describing Cassini Radio Science looking for Gravity waves. The Ka
band system has some issues in flight.
gives some numbers.. see page 19
the DSN antenna is on the order of 1E-15 at tau=1000 seconds if you're
careful, 1E-14 under normal operation
Tropospheric scintillation is also a factor..
I doubt we will ever see a telecom subsystem as complex and
sophisticated as Cassini's ever again. The modern trend is to less
redundancy, and higher level of integration in the boxes so fewer total
For the Juno mission on it's way to Jupiter, we were looking for the
radio's contribution to the measurement uncertainty being around 4E-16
at 1000 seconds.
https://www.youtube.com/watch?v=ulzq_mlU-fA is a high level explanation
of the gravity science
When the Deep Space Atomic Clock (a trapped Hg ion) flies, that will
change a lot of radio science, because we will be able to make more
accurate one-way measurements. They are hoping for an overall
improvement of 2 orders of magnitude.
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