NEW (Cont’d) NEW (SINCE 2010)

USNO Analysis Center Progress 2010-2

C. Hackman, V.J. Slabinski, J.C. Tracey and S.M. Byram

United States Naval Observatory, Washington DC USA

For more information: Christine Hackman, US Naval Observatory, 3450 Massachusetts Ave NW, Washington, DC 20392, USA. Tel: (202) 762-1428. e: christine.hackman@usno.navy.mil. Products online: http:/www.usno.navy.mil/USNO/earth-orientation/gps-products

r u

u u

r

AC HISTORY AND PRODUCTS

• AC since 1997

• Contribute rapid and ultra-rapid solutions

• NEW: Produce IGS Final Troposphere Estimates

• NEW: Testing GLONASS processing

• Products generated using Bernese GPS Software

• Statistics below: 6 Jan 2009 – 30 Jun 2012; 5-s filtered

10

20

30

40

50

60

2009 2010 2011 2012

MM

YEAR

MEDIAN WRMS, USNO ORBIT WRT IGS RAPID

rapid

ultra past

ultra pred

10

100

1000

10000

2009 2010 2011 2012

PS

YEAR

MEDIAN RMS, USNO CLOCKS WRT IGS RAPID

stdev, rapid

RMS, rapid

RMS, ultra pred

0

50

100

150

200

250

300

350

400

2009 2010 2011 2012

MIC

RO

AR

C S

EC

USNO MEDIAN ERP RMS WRT IGS FINAL

x rap

y rap

x ult past

y ult past

x ult pred

y ult pred

96.5

97

97.5

98

98.5

99

99.5

100

2009 2010 2011 2012

%

USNO ON-TIME SUBMISSION RATE

ultras

rapids

On-time rate. Rapids: 100% on-time rate

maintained. Ultras: ~99% on-time. 2012:

missed 11 submissions 3-6 Jun due to

unscheduled network outage. Offsite

backup operations would have mitigated.

Note: Dr. V. Slabinski has made numerous improvements to automation.

Pre-transfer comparison. USNO test troposphere solutions WRT existing IGS Final estimates, 28 Feb – 14 Mar 2011. (Byram et al., 2011).

CHAIR IGS TROPOSPHERE WORKING GROUP

• Dr. C. Hackman, chair

• WG goal: improve accuracy, usability of IGS tropo estimates

• 40 members recruited Fall 2011

• Charter revised Fall 2011

• Survey distributed Winter 2012

IGS FINAL TROPOSPHERE ESTIMATES (FTEs)

• USNO now produces IGS FTEs

• Operations transferred from JPL July 2011

• IGS FTEs dated 17 April 2011 and after generated by USNO

• Dr. Sharyl Byram, project manager

• mm-level RMS agreement in total delay/N gradient/E gradient achieved for 18 station/25 d test prior to operations transfer

• 300+ stations processed daily

• More info: Poster 06-01, Byram & Hackman

SUB-DAILY UTGPS (2011)

• Mr. J. Tracey, project manager

• UTGPS: GPS-based extrapolator of VLBI UT1-UTC measurements used to predict UT1-UTC

• Was generated daily using IGR

• Now generated 4*/d using IGU

• Enables USNO Earth Orientation Dept to predict UT1-UTC 4*/day

NEW STUDY: PPP WITH USU PREDICTS

• Predictions suitable for RT applications

• Initial study: concatenate predicted orbits, clocks, EOPs (no filtering)

• Do PPP with these, IGS Finals

• Sites: AMC2, NIST, USN3 (all USA), PTBB (DE), IENG (IT)

• 26 Mar - 1 Apr 2012 (MJD 56012-8)

• Obtain 7-9 cm position repeatability

• ~ 1 ns RMS time transfer wrt IGSF

• More info: Hackman et al. (2012b)

83

84

85

86

87

88

89

90

91

56012 56013 56014 56015 56016 56017 56018 56019

NS

MJD

NIST-AMC2 (147 km)

USU

IGS-P

IGS

USU-IGS RMS = 864, STDEV = 719, MEAN = 478 ps

503

504

505

506

507

508

509

510

511

512

56012 56013 56014 56015 56016 56017 56018 56019

NS

MJD

PTBB-IENG (835 km)

USU

IGS-P

IGS

USU-IGS RMS = 1016, STDEV = 1007, MEAN = -131 ps

FUTURE PLANS

• Improve PM, no. stations, rapid clocks.

• Develop off-site backup operation.

• Incorporate GLONASS into IGS submissions.

• Troposphere: perform Repro 2; incorporate WG recommendations.

-6

-5

-4

-3

-2

-1

0

1

56012 56013 56014 56015 56016 56017 56018 56019

NS

MJD

USN3-AMC2 (2361 km)

USU

IGS-P

IGS

USU-IGS RMS = 902, STDEV = 900, MEAN = 55 ps

-517

-515

-513

-511

-509

-507

56012 56013 56014 56015 56016 56017 56018 56019

NS

MJD

USN3-PTBB (6275 km)

USU

IGS-P

IGS

USU-IGS RMS = 1474, STDEV = 1417, MEAN = 407 ps

1

10

100

1000

0 1 2 3 4 5 6

RM

S, M

M

SITE (1=AMC2, 2=NIST, 3=USNO, 4= PTBB, 5=IENG)

COORDINATE REPEATABILITY

N-PPU

E-PPU

H-PPU

N-PPI

E-PPI

H-PPI

MEDIAN: 72, 80, 93 mm (N, E, H PPU); 3, 6, 6 mm (N, E, H PPI)

0.0001

0.001

0.01

0.1

1

0 2000 4000 6000 8000

RM

S, M

M

DISTANCE (KM)

SITE A TO B: REPEATABILITY vs LENGTH

DN-PPU

DN-PPI

DE-PPU

DE-PPI

DH-PPU

DH-PPI

DL-PPU

DL-PPI

MEDIAN: 74, 150, 160, 165 mm (dN, dE, dH, dL PPU); 4, 8, 6, 7 mm (dN, dE, dH, dL PPI)

GLONASS PROCESSING

• Test adding GLONASS data to network processing

• Dr. S. Byram, project manager

• Rapid products generated/tested since Winter 2012

• One result: adding GLONASS data reduces z-axis rotation wrt IGR

• Findings presented at ION PLANS 2012 (Byram & Hackman, 2012c)

• Ultra-rapid products to be completed Summer 2012

• See Poster 10-02, Byram & Hackman, for more details

Timing results. USU = PPP results obtained using USNO predicted values; IGS-P = PPP results using IGSF; IGS = IGS Final Clock values

Coordinate precision. PPU, PPI = PPP results obtained using USNO predicts or IGS Finals. PPU coordinate precision is 7-9 cm; no cancellation of errors with subtraction. (Not shown: PPI, PPU agree well within RMS).

Polar motion & LOD. PM (left): Rapids: Median RMS 134-191 marc sec wrt IGS

Final; note 2012 improvement. Ultras: Median RMS 134-217 mm wrt IGS Final, post-

processed portion; 304-376 mm for 24-h predict. LOD (right): Rapids: Annual RMS

residual 16-19 ms wrt IGR.

14.5

15

15.5

16

16.5

17

17.5

18

18.5

19

19.5

2009 2010 2011 2012

MIC

RO

SEC

USNO RAPID LOD RESIDUAL WRT IGS RAPID

2010-2 IGS-Related Bibliography S. Byram & C. Hackman, Computation of the IGS Final Troposphere Product by the USNO, Poster 06-01, 2012 IGS Workshop, Olstzyn, Poland, 2012a.

S. Byram & C. Hackman, GNSS-Based Processing at the USNO: Incorporation of GLONASS Observations, Poster 10-02, 2012 IGS Workshop, Olstzyn, Poland, 2012b.

S. Byram & C. Hackman, High-Precision GNSS Orbit, Clock and EOP Estimation at the United States Naval Observatory, Proc. 2012 IEEE/ION Position Location and Navigation Symposium, 5 pp, in press, 2012c.

S. Byram, C. Hackman & J. Tracey, Computation of

a High-Precision GPS-Based Troposphere Product by the USNO, Proc. ION GNSS 2011, 572-578, 2011.

C. Hackman, V.J. Slabinski, J.C. Tracey & S.M. Byram, USNO Analysis Center Progress 2010-2, Poster 10-07, 2012 IGS Workshop, Olstzyn, Poland, 2012a.

C. Hackman, S.M. Byram, V.J. Slabinski & J.C. Tracey, Near-Real-Time and Other High-Precision GNSS-Based Orbit/Clock/Earth-Orientation/Troposphere Parameters Available from USNO, Proc. 2012 ION Joint Navigation Conference (JNC), 15 pp, in press, 2012b.

C. Hackman, S. Byram, V. Slabinski & J. Tracey, United States Naval Observatory Analysis Center Report 2011, IGS Technical Report 2011, 6 pp, in

press, 2012c.

C. Hackman & S. Byram, IGS Troposphere Working Group 2011, IGS Technical Report 2011, 6 pp, in press, 2012d.

C. Hackman & D. Matsakis, Precision and Accuracy of USNO GPS Carrier Phase Time Transfer: 2012 Update, Proc. IEEE International Frequency Control Symposium (IFCS), 6 pp, in press, 2012e. C. Hackman, High-Precision Low-Latency GPS-Carrier-Phase-Based Satellite Orbits, Clocks and Geophysical Parameters Available from the USNO, Proc. 2011 ION JNC, 1163-1177, 2011a.

C. Hackman & D. Matsakis, Precision and Accuracy of USNO GPS Carrier Phase Time Transfer: Further Studies, Proc. 2011 Joint Conference, IEEE IFCS &

European Frequency and Time Forum, 1046-1051, 2011.

C. Hackman, Impact of Network De-Densification on GPS-Estimated Polar Motion: a Simulation Study, European Geosciences Union General Assembly. 2011b.

C. Hackman & D. Matsakis, Accuracy and Precision of USNO GPS Carrier Phase Time Transfer, Proc. 42nd Ann. Precise Time and Time Interval (PTTI) Systems and Applications Meeting, 16 pp, 2010. C. Hackman, V. Slabinski, J. Tracey, S. Byram & B. Luzum, The USNO Analysis Center: Progress, Problems and Future Expansion, International GNSS Service (IGS) Workshop, Newcastle, England, 2010.

Improved z-axis orientation. Z-axis rotation wrt IGR orbit. Control = GPS only; RMS = 104 mas. GNSS = GPS+ GLONASS; RMS = 76 mas. 23 Feb – 7 Jul 2012.

Orbits & clocks. Orbits (left): Rapids: Median WRMS 14-17 mm wrt IGR. Ultras:

Median WRMS 19-21 mm wrt IGR, post-processed portion; 44-49 mm for 6-h predict.

Clocks (right): Rapids: Median standard deviation/RMS of 52-59/124-145 ps wrt IGR.

Ultras: 6-h predict has 2286-2862 ps median standard deviation wrt IGR. Internal

studies indicate difficulty predicting Block IIA clocks (Hackman et al. 2012b).