Author Topic: NASA - Voyager 1 and 2 updates  (Read 76018 times)

Offline Sam Ho

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Re: NASA - Voyager 1 and 2 updates
« Reply #180 on: 08/11/2017 07:07 PM »
That still begs the question of whether NASA and the international community want to increase the southern polar DSN capacity.

Semi OT but is there operational advantages to having large arrays of smaller dishes (the VLA strategy) compared to having one big dish (the Arieebo strategy)?

Yes. With an array, you can use the antennas separately for "nearby" probes (e.g. Mars, allowing you to communicate with several probes simultaneously), and use them in an array only when you need to.
The end result of the DSN Aperture Enhancement Project will be five 34m antennae at each complex, and retirement of the 70m antennae.  An array of four 34m antennae works about as well as a 70m antenna, and is a lot easier to maintain.

So far, two 34m antennae (DSS-35&36) have been built in Canberra, and two more (DSS-56&53) are under construction in Madrid.

https://www.nasa.gov/directorates/heo/scan/services/networks/txt_daep.html
https://www.nasa.gov/directorates/heo/scan/services/networks/txt_daep_transition.html
https://www.nasa.gov/directorates/heo/scan/news_dss-36_operational.html
https://www.nasa.gov/directorates/heo/scan/services/networks/DSS53_DSS56_gallery

For Mars, you can also have multiple downlinks on one antenna.  (Mars is currently the only place with multiple spacecraft, but it could work elsewhere as well.)  Obviously, MSPA is not useful for the Voyagers.
Quote
1.6.5 Multiple Spacecraft Per Antenna (DSN)
Where a multiplicity of spacecraft lie within the beamwidth of a single DSN antenna, it may be possible to capture data from two or more spacecraft simultaneously using the Multiple Spacecraft Per Aperture (MSPA) system. MSPA decreases DSN loading and will save the project’s money (see Section 2.1.3).
https://deepspace.jpl.nasa.gov/files/dsn/6_NASA_MOCS_2014_10_01_14.pdf

Offline AegeanBlue

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Re: NASA - Voyager 1 and 2 updates
« Reply #181 on: 08/11/2017 10:39 PM »
Talking about the DSN is not entirely of topic with Voyager, since DSN's history is tied to the Voyager. The problem with DSN is that for most of its life it has not been a line item, rather upgrades to DSN were tied to a mission finding funding to pay for them. One of the 70 m antennas, I think the one at Goldstone, is known as the Apollo antenna because it was used to receive Apollo broadcasts from the Moon. The large antennas were originally built as 64 m antennas having the Parkes Observatory as their model during the Apollo era and upgraded to 70 m in the 1980s for Voyager's flyby of Uranus. Voyager, built with 1970s technology and pretty far away does need large antennas just for receiving. It's storage capacity, both in tape and computer memory is quite limited, and it is so far that its slowest playback capacity is faster than what it can transmit. Back in the 1980s it transmited pictures in real time because they were too big to store a sufficient number on board, hence the need to upgrade the antennas. New Horizons has a weaker transmitter but a much larger storage capacity, during the encounter it mostly took observations and stored in its solid state recorder 200 times the data that Voyager 2 returned from Neptune. New Horizons can likely be programmed to store its data and transmit it in bursts when it gets too far away, and during those bursts they can likely array all DSN antennas to receive the data. After New Horizons there is simply no new mission beyond Neptune even on a decadal survey, and please correct me if I am wrong. I have been looking on the mission concepts presentations of LPSC and the most recent mission concept I remember for a mission beyond Neptune was a study on how one would work with the SLS, and that was 5 years ago. As far as I know neither heliophysics nor planetary science has such a mission as either a flagship or mid range, and it most certainly doesn't fit on a Discovery budget. I remember that once Alan Stern submitted a Discovery proposal for Pluto on a Titan and it was shot down by NASA HQ because they did not intend to pay for the most expensive launcher for Discovery.

Offline Sam Ho

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Re: NASA - Voyager 1 and 2 updates
« Reply #182 on: 08/12/2017 02:28 AM »
As I mentioned a few posts ago, Voyager 1 still conducts a Digital Tape Recorder playback about once every two months, using a 70m+34m antenna array.

The Voyager telecommunication system has a fairly limited set of choices at low rates. The slowest DTR playback rate is 1400bps. Below that is 160bps real-time science, which is currently the main mode used, and then 40bps engineering.

https://descanso.jpl.nasa.gov/monograph/series13/DeepCommo_Chapter3--141029.pdf

By contrast, New Horizons is much more flexible. NH can send telemetry at speeds down to 6bps, and the solid state recorder does not have a minimum playback speed. While the burst mode you suggest is certainly possible, it would be much easier to stream data slowly at whatever rate the link supports for however long it takes. NH took 15 months to send back the Pluto encounter data, at a data rate of around 1kbps.

Offline Star One

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Re: NASA - Voyager 1 and 2 updates
« Reply #183 on: 08/18/2017 11:53 AM »
How Nasa's Voyager spacecraft changed the face of UK science

Quote
Hunt himself was such a regular on Patrick Moore’s The Sky at Night television show, that he became the public face of the mission to a whole generation of UK armchair astronomers.

And it is not just the public perception of space that was changed by the Voyager images. “In those days planetary exploration was something that Nasa did and the UK didn’t really get involved in. But the fact that Garry was involved meant that other people could get involved. This has blossomed now if we think of missions like Rosetta and Cassini and the forthcoming Juice mission, all with massive UK involvement. It made us think that the UK does planets, Europe does planets – it’s not just Nasa,” says Murray.

Indeed, the United Kingdom Space Agency’s website lists 14 planetary exploration missions that the UK is working on. Most of these are through its membership of the European Space Agency. And it all started with the Voyagers.

“I think about Voyager all the time because they were the pathfinders essentially. They taught us how to send multi-instrument spacecraft to the outer solar system,” says Murray.

https://www.theguardian.com/science/across-the-universe/2017/aug/18/how-nasas-voyager-spacecraft-changed-the-face-of-uk-science

Offline catdlr

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Re: NASA - Voyager 1 and 2 updates
« Reply #184 on: 09/01/2017 03:54 AM »
Voyager 2 Trajectory through the Solar System

NASA
Published on Aug 31, 2017

This visualization tracks the trajectory of the Voyager 2 spacecraft through the solar system. Launched on August 20, 1977, it was one of two spacecraft sent to visit the giant planets of the outer solar system. Like Voyager 1, Voyager 2 flew by Jupiter and Saturn, but the Voyager 2 mission was extended to fly by Uranus and Neptune before being directed out of the solar system.

To fit the 40-year history of the mission into a short visualization, the pacing of time accelerates through most of the movie, starting at about 5 days per second at the beginning and speeding up to about 11 months per second after the planet flybys are passed.

The termination shock and heliopause are the 'boundaries' created when the plasma between the stars interacts with the plasma flowing outward from the Sun. They are represented with simple grid models and oriented so their 'nose' is pointed in the direction (Right Ascension = 17h 24m, declination = 17 degrees south) represented by more recent measurements from other missions.

Credit: NASA's Scientific Visualization Studio
https://svs.gsfc.nasa.gov/4140

https://www.youtube.com/watch?v=l8TA7BU2Bvo?t=001

Tony De La Rosa

Offline catdlr

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Re: NASA - Voyager 1 and 2 updates
« Reply #185 on: 09/01/2017 03:57 AM »
Voyager 1 Trajectory through the Solar System

NASA
Published on Aug 31, 2017

This visualization tracks the trajectory of the Voyager 1 spacecraft through the solar system. Launched on September 5, 1977, it was one of two spacecraft sent to visit the giant planets of the outer solar system. Voyager 1 flew by Jupiter and Saturn before being directed out of the solar system.

To fit the 40-year history of the mission into a short visualization, the pacing of time accelerates through most of the movie, starting at about 5 days per second at the beginning and speeding up to about 11 months per second after the planet flybys are passed.

The termination shock and heliopause are the 'boundaries' created when the plasma between the stars interacts with the plasma flowing outward from the Sun. They are represented with simple grid models and oriented so their 'nose' is pointed in the direction (Right Ascension = 17h 24m, declination = 17 degrees south) represented by more recent measurements from other missions.

https://svs.gsfc.nasa.gov/4139
Credit: NASA's Scientific Visualization Studio

https://www.youtube.com/watch?v=qYNIsgDrIRE?t=001

Tony De La Rosa

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Re: NASA - Voyager 1 and 2 updates
« Reply #186 on: 09/06/2017 04:56 AM »

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