NASATests e-VLBI concept from the Madrid Deep

Space Network to JPL

Thom Stone

Principal Computer ScientistCSC-NASA Ames Research Center

Deep Space Network and eVLBI

• What is “electronically linked-Very Long Baseline Interferometry” and why do we need it?

• What is the DSN and how is it connected now?

• Our testing, why, when how • Results• Conclusions and suggestions• Data from deep space - The future

What is e-VLBI

• eVLBI is the process of using high speed networks to connect radio telescopes separated by large distances (100-1000s of km) instead of the traditional method of recording onto magnetic tape and shipping the recorded data to a central correlator

• In other words several radio telescopes dispersed over the planet are tied together over high speed networks to form one big telescope.

Arecibo radio telescope(Puerto Rico)

• World’s largest single-dish radio telescope • 305m diameter, 40K perforated aluminum panels

e-VLBI

• Tried over European networks successfully 2007

• Requires the high available bandwidth of a advanced commercial or research network

• Main application is tracking spacecraft and other objects in deep space (triangulation)

• Requires exacting time synchronization between telescopes (1013 sec.)

• Logical method for creating large array

What is the NASA Deep Space Network (DSN)?

• Three arrays of radio telescopes (dish antenna) spread around the world to give maximum sky coverage

• Used to contact spacecraft beyond earth orbit both NASA and International

• TDRSS satellites are used to communicate to spacecraft in Earth orbit

Deep Space Network Ground Stations:•Near Barstow California in the Mojave desert•Outside of Madrid Spain•In Parks Australia

Why the DSN

• Each station has many antenna including one 70 meter to:– Send Beatles songs to other star system– Tracking, commanding, and receiving data from

spacecraft (NASAs and International partners) outside of Earth orbit. Some are light hours away

– Some radio Astronomy

Current DSN connectivity

• Minimal Internet connectivity at each site even though they are near major high speed research networks(as well as commercial networks)

• Use leased lines and tapes to move data to NASA centers and then on to researchers

NREN-Madrid-JPL Test

• Took place in December 2006 after several months of discussion and design

• Goal was to form eVLBI between Madrid and Goldstone DSN stations with a Beowolf cluster (JVC) at JPL as correlator

• Object was to demonstrate that data now sent on tapes to JPL could utilize HPREN (High Performance Research and Education Networks) instead (faster, and better)

• Cooperation between JPL, ARC, REDIRIS, and the DSN

• Up to a terabyte a day can be generated in Madrid

JPL Correlator (Beowulf Cluster)

Limiting Factors

• There is only an E1 link (2 Mb/sec) between Madrid DSN and REDIRIS the Spanish HPREN in downtown Madrid

• The default route to JPL from RedIRIS is via commercial network not NREN’s 1 Gbps link

• The software/hardware (MARK-5 system) used to make tapes was not set up for high speed transmission of the data

Test Set Up

• A “Mark-5” computer, used to generate files from data received from the antenna from spacecraft was moved to the REDIRIS operations center on a Gigabit LAN segment

• Success criteria was to prove that 1/2 Tbyte could be moved in 18 hours or less (about 60-100 mbits per second with TCP average)

• A Route was set up between the Mark-5 computer at REDIRIS to the Columbia Supercomputer

• UDP and TCP tests were performed between hosts – Between hosts on the same LAN segment– Between hosts on the wide area– Using the Mark-5 software

• Mark-5 connected to RedIRIS LAN (1 Gbps)

• RedIRIS connects to GEANT (European backbone) 1 Gbps

• GEANT Spain to GEANT France to transatlantic cable (10 Gbps)

• GEANT to Abilene (10 Gbps)• Abilene to NREN (10 Gbps)• NREN would need to set up route

from RedIRIS to machine at JPL for real test

• 40km Madrid to RedIRIS: work in progress

Route

Test Results

• Used IPERF etc. for testing• Able to get up to 800 Mbps UDP with a

few errors from Spain (RedIRIS) to ARC. Less loss ARC->Spain

• Got 60-90 Mb/sec TCP depending on time of day without optimization

• Unable to move files using MARK-5 software

Conclusion and Suggestions

• This is a viable concept, data can be moved faster and cheaper

• Improvement can be made with Jumbo Frames and multi-stream or other fast TCP

• Host tuning is a must• A great candidate application for scavenger

(less than best effort) service

What’s Up

• European VLBI up and working• 40 KM Link from Madrid DSN to RedIRIS not

funded even though pricing cheaper than low speed point to point to JSC/JPL

• Reason is funding and distrust of IP networks by some in NASA

• Whole DSN in need of upgrade to support future space exploration

What’s Next

• Keep requesting funding for high speed links to HPRN from all three DSN sites

• New NASA lunar endeavors will require higher data rates and faster access to data sooner rather than later

Un-Indicted Coconspirators

• "Garcia Miro, Cristina"

• <CGMiro@mdscc.nasa.gov>

Un-Indicted Coconspirators

• " Fernando Aragon" FAragon@mdscc.nasa.gov• "Cristina Garcia Miro" CGMiro@mdscc.nasa.gov• "Raul Alonso" <RAlonso@mdscc.nasa.gov>• "Charles J. Naudet” Charles.J.Naudet@jpl.nasa.gov• “Tom Kuiper” kuiper@jpl.nasa.gov• John.E.Clark@jpl.nasa.gov• Ken Freeman, Ray Gilstrap, Hugh Lamaster at ARC• Others at Madrid DSN and JPL

Thank youQuestions? Comments?

Thom Stone

NASA Ames Research Center / CSC

thom.stone @ nasa.gov