The VLBI2010 Broadband System: First Geodetic … VLBI2010 Broadband System: First Geodetic Results Reported by Arthur Niell MIT Haystack Observatory IVTW - 2012 October 22 Haystack

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Haystack 12012 October 22 1

The VLBI2010 Broadband System: First Geodetic Results

Reported by Arthur NiellMIT Haystack Observatory

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Haystack 22012 October 22

GGAO12M Development TeamChris Beaudoin

1

, Bruce Whittier1, Mike Titus1, Jason SooHoo1, Dan Smythe1, Chet Ruszczyk

1, Alan Rogers1, Mike Poirier1, Arthur Niell1, Russ McWhirter

1, Alan Hinton1, Brian Corey1, Jon Byford, Alan Whitney

1

Chopo Ma

2

Ed Himwich3, Tom Clark3

Jay Redmond4, Skip Gordon4, Mark Evangelista4, Irv Diegel4, Paul Christopolous

3

Wendy Avelar

5, Chuck Kodak5, Roger Allshouse

5, Katie Pazamickas

5, Ricky Figueroa

5

1

MIT Haystack Observatory, 2

NASA GSFC,3

GSFC/NVI ,4

HTSI, 5

ITT

Science driver

Accurate terrestrial and celestial reference frames

1 mm position and 0.1 mm/yr velocity

Requirement for accurate sea level determination

Achieved by combination of VLBI, SLR, and GNSS

Next generation VLBI development

Fast slewing antennas to rapidly sample the atmosphere

High precision delay observable

Wide spanned bandwidth: 2 –

14 GHz

Four bands and two polarizations

High data rate: 8 Gbps

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Background

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12m antenna at Goddard Geophysical and Astronomical Observatory, Greenbelt, Maryland

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Haystack 52012 October 22 5

~ 2.2 – 15 GHz Spanned RF Bandwidth

OLDOLD

Phase

Frequency (GHz) 142

Observing Frequency Bands

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Odd channels from each pol’n for one band output to each Mk5C.

2 Gigabits/sec recorded on each Mk5C.

Total data rate: 8 Gbps

Feed and LNAs cooled to ~20K

Both senses of linear polarization usedAntenna

Control room

RF filterphase/noise cal

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Caltech supplied

QRFH feed

2-12 GHz LNAs

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Westford QRFH feed

All backend equipment in one rack

Picture (oops! DBE compatibility test in progress)

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Broadband 8 Gbps Rack

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GGAO12M SEFD -

2012 May

Dewar (~20K)

QRFH feed

Two broadband LNAs

Couplers for phase and noise cal injection

Phase cal

5 MHz spacing

Use all tones for each channel to obtain delay correction

Noise source for Tsys

80 Hz switching controlled by RDBE

Not implemented for these observations

RF to control room over optical fiber

Caused implementation delay because manufacturer did not meet advertised specs

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Signal Chain Frontend

UpDown

Converter

Select frequencies and Nyquist

zone (NZ2 used)

Band frequencies (lower edge)

3.2 GHz, 5.3 GHz, 6.3 GHz, 9.3 GHz

Band width 512 MHz

RDBE

Joint NRAO-Haystack development (also in use at VLBA)

PFB: 32 MHz channels (sub-bands)

Record eight horizontal and eight vertical polarization channels

2 Gbps

data rate

Mark5C recorder

2 Gbps

1 module

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Signal Chain Backend

Schedule using sked (simplified)

Select sources, band frequencies, SNR target per band

Specify scan parameters and antenna characteristics

Push GO to generate 24 hour schedule

Observing

Convert sked output to scripts for controlling RDBEs

and Mark5Cs

Make usual checks of frequencies and time (but four sets!)

Antenna is run by Field System

RDBEs

and Mark5Cs are run from scripts until Field System ready

Quantization threshold set for each scan by script

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Geodetic Session Components

Correlation and observable estimation

DiFX

Difx2mark4

fourfit

coherent fit to 4 bands*2 polarizations + ionosphere

Geodetic estimation

nuSolve

with stochastic processes for atmosphere and clocks

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Geodetic Session Components

2012 May six hour session

30 scans/hour

30 second scans

50 source s ≥

0.6 Jy

Median formal delay error ~0.5 psec

Scaled delay error ~3 psec

(1 mm)

Position estimation for GGAO12M

Delay residual RMS using νSolve 10 psec

Position uncertainties ~ 2/3/9 mm in E/N/U

Probably atmosphere dominated

Phase cal delay variation in azimuth of 4 psec

Possible 0.5 mm horizontal position error

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Results

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External sources of RFI

Usual S-band sources

Unknown 4 GHz at GGAO (NSA or CIA?)

Local comm

link at 6 GHz at Westford

Intra-technique RFI for geodetic Core Sites

Satellite Laser Ranging aircraft avoidance radar at 9.4 Ghz

Potential to damage LNAs

Must keep pointing direction 90º

apart

Coordinated observing appears difficult

Attempting to mitigate by physical blockage near radar

DORIS transmission near 2 GHz

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RFI

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Sky coverage no mask

0

30

60

90

60

30

0

030609060300

Observations from schedule file ./12279o.skd for experiment 121005 ( 774 scans)

WESTFORD (Wf) 774 scans0

30

60

90

60

30

0

030609060300

Observations from schedule file ./12279o.skd for experiment 121005 ( 774 scans)

GGAO7108 (Gg) 774 scans

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Sky coverage mask on

0

30

60

90

60

30

0

030609060300

Observations from schedule file ./12278d.skd for experiment 121005 ( 785 scans)

WESTFORD (Wf) 785 scans0

30

60

90

60

30

0

030609060300

Observations from schedule file ./12278d.skd for experiment 121005 ( 785 scans)

GGAO7108 (Gg) 785 scans

2012 October 4-5

Two six hour sessions

34 scans/hour

30 second scans

SLR radar active on Oct 4; mask on

SLR radar off on Oct 5; mask off

Fringes both days

Both days correlated on Mark4; only three phase cal tones/channel

No post-correlation processing will be done till correlated on DiFX

Anxiously awaiting results to look at baseline repeatability

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Results

12m antenna

Install motorized positioner

for Dewar/feed/LNA package

Implement noise cal for Tsys

Signal chain

Replace 4 RDBEs

by 2 quad-RDBEs

(4 IFs

per ROACH)

Replace 4 Mark5Cs by one Mark 6

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Next steps

Broadband system

Successful implementation on the 12m antenna

Broadband RF from 2 –

12 GHz achieved with QRFH and two LNAs

Obtained anticipated sensitivity of 2500 Jy

for SEFD

Phase calibration allows phase connection over full range of frequency

Obtained anticipated delay precision of less than 4 picoseconds

Operations

UDC/RDBE/Mark5Cs operated remotely

Geodetic sessions run unattended after setup

Correlation/post-processing

DiFX

correlation

Coherent fitting of four bands dual polarization with ionosphere

estimation

Full end-to-end geodetic observations IVTW -


Summary

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Haystack2012 October 22

Courtesy Wendy Avelar

24

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RDBE-Q

Input four 512 MHz IFs

Output 2 x 2 Gbps

(current geodesy mode) or 2 x 4 Gbps

Output in VDIF with complex samples

Tested with test vector generator and test tone inputs

Mark6

8 Gbps

to one module (now)

Anticipate first observations in December

RDBE-X

Design begun (Haystack and Petrachenko)

ROACH2 based

Four 1 GHz IFs

16 Gbps

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Signal chain development

GGAO12M

Elevation motion –

problem has not returned

Phase cal peculiarities –

most of system to be replaced

Positioner

Moves under motor control

Dewar holds vacuum

Testing for cooling right now

Install on 12m mid-November

Westford

QRFH feed and new hardware in Dewar performed well

Tsys

~ 30K

Efficiency very low

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Haystack-NASA VGOS Systems

Kokee

20m

Haystack will install signal chain by next summer if observing permits

Kazan

Proposal for 12m with Broadband Signal Chain submitted by HTSI and Haystack

Too expensive, so fall back to Intertronics

S/X feed and LNAs

Receiver and formatter/recorder not discussed yet

USNO

Expect RFP within a month for 12m at Kokee

NASA Request for Information (RfI) for Core Sites (up to 10)

Response by HTSI/Haystack for combined VLBI/SLR/GPS/DORIS

Separate response by Haystack to provide VLBI systemIVTW -


Other VGOS development

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Geodetic VLBI Highlights

VLBI2010 broadband system at GSFC

12m antenna with all major components

First geodetic session scheduled, observed, and correlated

DiFX

correlator

and fourfit

Developing new capabilities for broadband operation

Coherent fitting across polarizations and bands

Correlation of mixed channel widths , e.g. 8 MHz/32MHz

Mark6 recorder

16 Gbps

will reduce four recorders to one

Kazan University VLBI2010 signal chain (proposed)

May be second operational system

Cooperative development with HTSI (Honeywell)

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Program Overview

NASA (2010-2014)

Engineering

Operations

Research and development

Technique improvement/science

USNO correlator

(2009-2012 (2013 likely))

Engineering and development

Operations backup

USNO VLBI2010 implementation (-2012)

VLBI2010 signal chain for Kokee

20m antenna

Kazan University VLBI2010 signal chain (proposed)

Sub-contract to HTSI for 12m antenna

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NASA Contract

Engineering support

Field station diagnostics and repair

Analyse

station performance from correlator

results

Respond to problems from stations

Maintain spares depot; repair modules; ship replacements

Develop replacement equipment

Correlator

development (Mark4 and DiFX)

Operations

Mark4 and DiFX

correlators

R&D and Reference Frame sessions

New broadband data

Westford antenna

GGAO12M

Other sites as needed

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NASA Contract (cont’d)

Research and development

Frontends (Cryogenic feeds and amplifiers)

Receivers (RF to video)

Digital backends

Recorders

VLBI2010 broadband system

12m antenna at Goddard Space Flight Center

Broadband system on Westford

Technique improvement and science

RFI mitigation

Observation planning

Atmosphere

Radio astronomy ‘effects’

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Other Active Contracts

USNO: Washington Correlator

engineering support

through 2013 probably

Maintenance of Mark4 hardware correlator

Haystack correlator

as backup

USNO: VLBI2010 signal chain implementation

UpDown

converters, RDBEs, and Mark5Cs –

1st

contract

Dewar/feed/LNAs/calibration box, optical fiber links –

current

Installation on Kokee

20m antenna

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Potential Contracts (cont’d)

Kazan University (Russia) VLBI2010 system (proposed)

Will be under a contract from HTSI

New 12m to be purchased from Intertronics

Antennas

HTSI (Honeywell) responsible for everything else

Haystack to provide the broadband signal chain and checkout of geodetic VLBI functionality, first in US then in Russia

Moscow State University (Russia) VLBI2010 systems

HTSI: same arrangement

Proposal under discussion

GSI (Japan)

Interest in obtaining front end (Dewar/LNAs/feed)

Others interested in VLBI2010 Signal Chain

Norway, Sweden, Spain/Azores/Canary Islands

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NASA Geodesy and Haystack

Motivation for new system development (IVS WG3)

Replace aging antennas

Improve accuracy to 1 mm

Provide for continuous, unattended operation

Resulted in VLBI2010 specifications

Background for Haystack involvement

Provided majority of data acquisition systems for global program

Significant contributions to atmosphere and astronomy modeling

2012 October 22 IVTW -

Haystack37

http://ivscc.gsfc.nasa.gov/about/wg/wg3/IVS_WG3_report_050916.pdf

ftp://ivscc.gsfc.nasa.gov/pub/m isc/V2C/TM-2009-214180.pdf

http://ivscc.gsfc.nasa.gov/about/wg/wg3/

Limiting error sources

Varying atmosphere delay

Sensitivity

Strategy

Use fast-slewing antennas (5º/sec-12º/sec slew rate)

Obtain delay sensitivity through high data rate and wide spanned

bandwidth (Broadband Delay)

Design goals

Antennas of ≥

12m diameter

Data rates ≥

8 Gbps

using four bands of 0.5 GHz to 1 GHz each

Spanned bandwidth 2.2 GHz to ~14 GHz: delay uncertainty ~4 psec

BUT maintain observing compatibility with current S/X systems

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VLBI2010 development

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VLBI2010 signal chain

Cooled broadband QRFH feed and LNAs

Purchased from Caltech

Tested and packaged by Haystack

Phase and noise calibration

Phase cal generator developed by Haystack

Packaged by HTSI

UpDown

Converters (4) (Haystack)

In use for 2-12 GHz

Possible extension to 2-14 GHz (or higher)

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VLBI2010 signal chain

RDBE digital back end (4)

Developed by NRAO and Haystack

Produced by Digicom

(California)

In use by VLBA and NASA

Mark5C recorder (4) (Conduant)

In use by VLBA and NASA

In use by EVN

Mark6 recorder (1) (Conduant)

Up to 16 Gbps

from four 4 Gbps

inputs

Will replace 4 Mark5C recorders

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VLBI2010 correlation/processing

Correlation on DiFX

software correlator

Four separate correlations (four bands)

Working on 8MHz within 32MHz correlation for compatibility with legacy S/X systems

Post-correlation processing

difx2mark4 –

convert native output to Mark4 input

fourfit

Coherent fit across bands and polarizations while estimating ionosphere

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VLBI2010 Status

12m system

Operational at Goddard Space Flight Center

Using deliverable equipment

Some components not tested or not implemented

First geodetic observing session just completed

Westford

Using deliverable equipment

Low efficiency (≤

20%) above 5 GHz not understood

Kokee

20m

Most of signal chain completed

Funding/mechanism for mounting Dewar unclear

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NASA Space Geodesy Project (SGP)

Project level at NASA Headquarters

Viewed within NASA HQ as best way to get support and funding

Planning for ten sites

Not all in North America

Haystack involvement

Short term requirements

Complete and document 12m broadband system

Potential role of Haystack in SGP future

Not known at this time

Role of Haystack outside of SGP

Expected to continue as currently defined

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Current Technical Development

Mark6

RDBE

RDBE-Q (four 512-MHz bands per ROACH)

RDBE-V (two 1-GHz bands per ROACH)

Future: four 1-GHz bands per ROACH

MCI (complete monitor and control)

RFI mitigation

Vector Tie System

High speed networking (real-time and e-xfr)

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Technique Improvement

Implement end-to-end scheduling/analysis capability

Develop improved atmosphere modeling

Study effect of radio source structure

Analysis, modeling, and delay correction

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Astro/Geo Common Dev’ment

Shared goals (simplified)

Improve sensitivity

Increase data storage capacity

Differences

Astronomy –higher frequency for better angular resolution

Geodesy –

wider spanned bandwidth for better delay sensitivity

Astronomy –

campaign observing few times per year, several antennas

Geodesy –

sustained observing several times per week, many antennas

Astronomy –

mobilize personnel & equipment for limited time with close to best possible capability

Geodesy –

operational reliability through less than best achievable performance

Unique measurements by VLBI

Earth rotation angle (time): UT1-UTC (keep GPS up)

Scale of terrestrial reference frame: sea level change

Nutation: (e.g.) dynamics of the Earth’s core

Mandate to NASA for accuracy improvement

National Research Council decadal survey

1 mm position and 0.1 mm/year velocities

Implementation proposed through Space Geodesy Project

VLBI, SLR, GPS, and DORIS

Unified station

Vector ties among techniques to 0.1 mmIVTW -


VLBI geodesy

Observations

One or two scans per minute scattered around the sky

Scan lengths only long enough to get necessary SNR

Duty cycle only about 1/3 so can use burst mode to maximize instantaneous data rate.

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VLBI2010

Antenna and data acquisition

Cooled broadband frontend 2 –

14 GHz

Flexible RF to IF frequency conversion

Digital backends

High data rate recorder(s)

DiFX

software correlator

Extract all phase-cal tones

Correlate 8 GHz S/X legacy data and 32 MHz broadband channels

Post-correlation

Coherent fitting of all polarizations

Estimate differential ionosphere

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VLBI2010 System

Haystack as supplier

Worked with Digicom

to make RDBE available

Working with Conduant

to make Mark6 available

Building Dewar assembly and UDCs

Complete for USNO 20m this year

Kazan University through HTSI (proposed)

Potential customers

Moscow U

GSI Japan

Auscope, other Patriot 12m

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VLBI2010 Implementation

Instrumentation development

Digital back end

1 GHz bandwidth (2*512 MHz)

Higher data rate per chassis (2 ADCs/ROACH)

Recorder: 16 and 32 Gbps

reliable recording

Increase spanned bandwidth

Haystack’s role in VLBI2010 implementation ?

Science

Atmosphere limitation –

turbulence and asymmetry

Radio source structure effects

VLBI-unique geophysical applicationsIVTW -


Going forward

Coherently fit all four bands and all four cross-hands for phase delay, amplitude, rate and differential ionosphere.

Incorporate source structure phase.May have to be incorporated in the coherent fit.

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Post-correlation

Four independent 512 MHz RF bands

Each recorded on separate Mark5C at 2 Gbps

(Mk5B fmt)

Two linear polarizations for each 512 MHz band

Each pol’n/IF becomes sixteen 32-MHz LSB channels.

The channel set to be recorded is selectable.

Half of the channels from each polarization are recorded.

Currently: H1 V1 H3 V3 …

H15 V15

Switch soon to non-redundant spacing

e.g. 1 2 4 7 9 13 14 15

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VLBI2010 Broadband System

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VLBI2010 signal chain (cont’d)

Mark6

16 Gbps

demonstrated on prototype

Replace four Mark5Cs with one Mark6

Hardware prototype to be delivered in next two months

Resilient file system development beginning

Will accommodate slow or failed disks

Control plane software development beginning

Hope to begin testing in two months

Quadridge Feed Horn (QRFH)

California Instit

ute of Technology Design

Sandy Weinreb Ahmed Akgiray

Bill Imbriale

2‐14 GHz Unbalanced Design One single‐ended port per polarization

Designed for Patriot

12m Antenna Shaped Optics

Adaptable to other antenna optics

Overcomes limitations of commercial quadridge designs

Have observed 60% efficiency on 12m antenna

2012 October 22 56IVTW -

Haystack

2012 October 22 57IVTW -

Haystack

12m performance

fiber link noise

Current

Mark4 (RCP)

6 S-band channels

10 X-band channels: 8 upper sideband plus lower sideband on outer two.

DBE (when S/X stations have them)

Probably 3 DBEs

(2 for X and 1 for S)

Single pol’n: 15 channels per DBE

Dual pol’n: 8 channels per pol’n

per DBE

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S/X System

Correlate all cross-hands

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Correlation –

DBE to DBE

Broadband to Mark4 cross-correlation

8 MHz Mark4 channels 14 USB + 2 LSB

32 MHz PFB channels LSB

May have multiple 8 MHz channels within 32 MHz channel

Each type to be correlated against both types in same scan

Polarization

Mark4 channels RCP

Broadband channels linear polarization

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Correlation –

Mk4 to DBE

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Mark4 vs

DBE8-MHz analog channels (Mark5A or Mark5B – one module) S1U

S2U

S3U

S4U

S5U

S6U

X1L

X1U

X2U

X3U

X4U

X5U

X6U

X7U

X8L

X8U

PFB 32 MHz channels (Mark5C - 3 modules Mk5B format)|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---| S-band (2 pol’n)

|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---| Xlow-band (512 MHz) (2 pol’n)

Xhigh-band (512 MHz) (2 pol’n) |---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|

Correlate Mark4 against both linear polarizations of the broadband system

X1L X1U X2U Mark4 (8 MHz)--------

--------

--------

RCP

PFB (32 MHz LSB)--------

--------

--------

--------

Vertical pol’n

--------

--------

--------

-------- Horizontal pol’n

0 frequency(MHz) 32

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Example of 8 MHz vs

32 MHz

Mark4 Mark4

PFB PFB

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Correlation

The VLBI2010 Broadband System: First Geodetic … VLBI2010 Broadband System: First Geodetic Results Reported by Arthur Niell MIT Haystack Observatory IVTW - 2012 October 22 Haystack

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