VieVS User Workshop

14 – 16 September, 2011

Vienna

VIE_MOD

Lucia Plank

2VieVS User Workshop 2011

PART I: theory

PART II: program/workflow

PART III: usage

VieVS User Workshop 2011 3

computed delay τ

c

kb

-=

adjustment (lsm)

observed delay • from NGS-card file, corrected for

ionosphere

I. THEORY

computed delay • Vie_mod

o-c

VieVS User Workshop 2011 4

I. THEORY

TRSGCRS bPNRWb

Geocentric Celestial Reference System

ITRS

BCRS

International Terrestrial Reference System

GCRS

Lorentz-transformation

BCRS

cbk

reta

rded

b

asel

ine

corr

.

in TT-frame

Barycentric Celestial Reference System

source

Lorentz-transformation

gra

vita

tio

nal

re

tard

atio

n

VieVS User Workshop 2011

adjustment (lsm)

observed delay • from NGS-card file, corrected for

ionosphere

I. THEORY

computed delay • Vie_mod

o-c

models+ EOP (oceanic & gravitational high frequency terms,

nutation corrections)+ solid Earth tides + troposphere delay (VMF / GMF / NMF)+ ocean loading (FES2004 / EOT08a / GOT00 / AG06)+ thermal antenna deformation+ axis offset+ atmosphere loading

5

partial derivatives dVAR

in TT-frame

VieVS User Workshop 2011 6

II. WORKFLOW0. INPUT FILES (scan, parameter, antenna, sources)1. EARTH ORIENTATION

read EOP | Interpolation | Add high frequency models | Ephemerides | Transformation matrix TRS-CRS | Source vector

2. STATION COORDINATESloop over scans

loop over stationsStation corrections (SET | ocean loading | atmosphere loading |

pole tide | station velocity) | tropospheric parameters end stations

3. COMPUTED DELAY loop over baselines

calculation of the time delay following the consensus model (incl. relativistic & gravitative corr.) | troposphere | axis offset | thermdef.

4. PARTIAL DERIVATIVESwrt. EOP | wrt. source coordinates | wrt. station coordinates | wrt.

Love and Shida numbers end baselines

5. STORE RESULTSend scans

6. SAVE (scan, parameter, antenna, sources)

VieVS User Workshop 2011 7

III. USAGE

8

III. USAGETRF:

• stored at: ../TRF/VTRF2008.mat

• station coordinates (TRS)

• reference epoch

• station velocities

• Other: - self-created TRF

- ../TRF/*.txt

- specified format

9

III. USAGE

CRF:

• stored at: ../CRF/ICRF2.mat

• right ascension ra

• declination de

• ++ (structure index, …)

• Other: - self-created CRF

- not finished yet

10

III. USAGE

Ephemerides:

• stored at: ../EPHEM/jpl_421.mat

• Earth, Sun, Moon, Planets

• remembered for 2nd run

(jpl_421_05SEP12XA_N004)

• not critical for “normal” VLBI

11

III. USAGEEarth Orientation Parameters:

• c04 08 (daily) series from the IERS webpage; ../EOP/C04_08_1962_now.txt; updates might be necessary;predefined EOP: ../EOP/*.txt; watch format

• dX, dY: include/exclude from c04 table; mainly contains FCN

• high frequency EOP• ocean tides: interpf;

table 8.2 (xp,yp) & 8.3 (ut) diurnal & semi-diurnal

• libration: table 5.1a (xp,yp) & 5.1b (ut)

DON‘T CHANGE ANYTHING, THEN YOU‘RE CONSISTENT WITH THE IERS CONVENTIONS !

12

III. USAGEInterpolation of EOP:

• lagrange: window of 4 data points

- tidal UT variations: removed before interpolation, re-added

• linear: interpolation between the midnight before and after observation time. For a session from 18:00 to 18:00 this means, that there are 2 a priori lines and a break at midnight.

13

III. USAGE

Precession/Nutation Model:

14

III. USAGE

Station corrections:

• hear more from Hana

• Thermdef:

[A. Nothnagel, J. of

Geodesy, 2008]

15

III. USAGE

Pressure and temperature:

• Met data from NGS-file

• GPT as backup

• External .trp files

16

III. USAGE

A priori troposphere gradients:

17

III. USAGE

Mapping function:

• for atmospheric corrections on the delay

• VM1: ../VM1/yyyy_VM1.matregular update!

• GMF: applied when no VM1 available

18

III. USAGE

Quality code limit:

• Accept observations <

or = limit

• Good quality

observations have

quality code 0

19

III. USAGE

External ionosphere correction:

20

III. USAGE

Cut-off Elevation angle:

• all observations below this local elevation [°, degrees] are skipped

21

III. USAGE

Outliers:

• use/dont‘t use outlier

file (chosen in init_qu)

22

III. USAGE

PUSH