Phase Centre Calibration of the Galileo Satellite Navigation Antenna IGS workshop 2017, Paris (France) Antennas & Biases Session F. Gonzalez (ESA) M. Söllner (Airbus) E. Schönemann (ESA) F. Dilssner (ESA) 05/07/2017 ESA UNCLASSIFIED - For Official Use
Summary 1. Introduction 2. Metadata information to correct phase measurements Antenna Phase Centre Offset (PCO) Antenna Phase Centre Variation (PCV) Antenna - User direction (attitude) Antenna Reference Point (ARP) Centre of Mass (CoM) 3. Galileo Metadata and IGS 4. Conclusions ESA UNCLASSIFIED - For Official Use ESA 05/07/2017 Slide 2
Introduction Galileo Antenna Metadata (θ,φ) Phase Centre Variation (E1, E5a, E5b, E5, E6) Phase Centre Offset (E1, E5a, E5b, E5, E6) Static Antenna Reference Point Centre of Mass Dynamic ESA UNCLASSIFIED - For Official Use ESA 05/07/2017 Slide 3
Introduction IGS Antenna data Dynamic Static Phase Centre Variation Ionosphere-free (E1-E5a) (θ,φ) Phase Centre Offset (E1, E5a, E5b, E5, E6) Antenna Reference Point Phase Centre Variation (E1, E5a, E5b, E5, E6) Static Centre of Mass Dynamic ESA UNCLASSIFIED - For Official Use ESA 05/07/2017 Slide 4
Antenna - types Two antenna types GSAT01xx - EADS CASA GSAT02xx - Thales Alenia ESA UNCLASSIFIED - For Official Use ESA 05/07/2017 Slide 5
Antenna chamber calibration Individual for each navigation antenna by manufacturer Directional in azimuth (Φ) and nadir (θ) Each single frequency bands (E1, E5a, E5b, E5, E6) ESA UNCLASSIFIED - For Official Use ESA 05/07/2017 Slide 6
Antenna Phase Centre offset (PCO) Farfield Sphere Segment with Radius r around MRP C MRP (α) from measurements in constant distance from MRP Delay pattern C FF on farfield sphere in distance r around MRP: C α, r = C α ( ) ( ) r FF MRP + R(α) r R(α 2 ) Range from PCO to sphere around MRP: " R α = r d! rˆ α ( ) ( ) R(α 1 ) PCO d MRP C dx = C dy = C dz = MRP MRP ( θ, ϕ) 2 2 sin θ cos ϕ MRP ( θ, ϕ) sinθ cosϕ sinθ sinϕ 2 2 sin θ sin ϕ ( θ, ϕ) cosθ C ( θ, ϕ) MRP 2 2 ( cos θ cosθ ) cosθ PCO: Find d, where R(θ) is most similar to C FF (θ,r)!! 2! Minimize res( d ) = ( C ( ) ( ) 2 PCO α, d CPCO α, d " " with C α, d = C α + d! rˆ α PCO ( ) ( ) ( ) MRP < > (weighted) averaging over α (field of view) Note, α represents the observation direction (off-axis angle θ and azimuth angle ϕ) ESA UNCLASSIFIED - For Official Use ESA 05/07/2017 Slide 7
Antenna Phase Center Variation (PCV) Azimuthal values [0,360 ] Zenith values from 0 to 14 (GSAT01) and 20 (GSAT02) All 5 single frequencies GALILEO-1 E11 E101 2011-060A TYPE / SERIAL NO CHAMBER ESA 1 09-FEB-12 METH / BY / # / DATE 2.0 DAZI 0.0 14.0 1.0 ZEN1 / ZEN2 / DZEN 5 # OF FREQUENCIES GALILEO-2 E18 E201 2014-050A TYPE / SERIAL NO CHAMBER ESA 1 12-FEB-16 METH / BY / # / DATE 5.0 DAZI 0.0 20.0 0.5 ZEN1 / ZEN2 / DZEN 5 # OF FREQUENCIES ESA UNCLASSIFIED - For Official Use ESA 05/07/2017 Slide 8
Antenna Phase Center Variation (PCV) Azimuthal values [0,360 ] Zenith values from 0 to 14 (GSAT01) and 20 (GSAT02) All 5 single frequencies (e.g. E1 signal). 4 2 GSAT0101 (IOV) GSAT0201 (FOC) 0 [millimetres] 2 4 6 8 0 2 4 6 8 10 12 14 16 18 20 ESA UNCLASSIFIED - For Official Use Nadir angle [deg] ESA 05/07/2017 Slide 9
Antenna - PCV Azimuthal components (GSAT01) ESA UNCLASSIFIED - For Official Use ESA 05/07/2017 Slide 10
Antenna - User direction (attitude) Azimuthal correction requires Satellite yaw modeling (e.g. GSAT0101) Orientation accuracy better than ground antennas 1 1 Source: F.Dilssner, Galileo IOV Spacecraft Metadata and Its Impact on Precise Orbit Determination, EGU2017 ESA UNCLASSIFIED - For Official Use ESA 05/07/2017 Slide 11
Antenna Reference Point Antenna integrated on body frame Physical point on the satellite [mm] X Y Z GSAT01 1375.5 600.0 1100.5 GSAT02 140.0 0.0 1215.0 ESA UNCLASSIFIED - For Official Use ESA 05/07/2017 Slide 12
Centre of Mass dry measurement in stow ESA UNCLASSIFIED - For Official Use ESA 05/07/2017 Slide 13
Centre of Mass tank filling ESA UNCLASSIFIED - For Official Use ESA 05/07/2017 Slide 14
Centre of Mass Solar array deployment ESA UNCLASSIFIED - For Official Use ESA 05/07/2017 Slide 15
Centre of Mass - Values Dynamic information. Value after any maneuver sent to ILRS Agreement between S/C well below 1 cm +X [mm] GSAT01 1206.0 1205.8 1205.6 1205.4 1205.2 1205.0 695 696 696 697 697 698 698 Mass [Kg] +X [mm] 320 310 300 290 280 270-01 -02 GSAT02 260 650 660 670 680 690 700 710 720 Mass [Kg] ESA UNCLASSIFIED - For Official Use ESA 05/07/2017 Slide 16
Metadata versus IGS Galileo (GSAT_wwww.atx) IGS (IGS14.atx) Source Measured on ground Estimated in space Types Frequencies Data-static Per single Satellite Single Frequency (E1,E5a,E5b,E5,E6) PCV PCO (θ,φ) PCO - ARP ARP - SRF per family (IOV,FOC-L3,FOC) Ionosphere-free (E1-E5a) PCV PCO (θ) Data-dynamic CoM - SRF PCO CoM Attitude Normal + Modified Normal Frame Satellite Reference Frame Antex ESA UNCLASSIFIED - For Official Use ESA 05/07/2017 Slide 17
Metadata versus IGS Accuracy of estimated in space affected by models accuracy (e.g. SRP) Estimated in Space using NAPEOS versus measured on ground 0.035 0.2 0.03 0.15 0.025 0.1 0.02 0.05 Metre 0.015 0.01 0.005 0-0.005-0.01 101 102 103 201 202 203 204 205 206 207 208 X Y Metre 0-0.05-0.1-0.15-0.2-0.25 101 102 103 201 202 203 204 205 206 207 208 Z ESA UNCLASSIFIED - For Official Use ESA 05/07/2017 Slide 18
Summary and conclusions Calibrated Metadata for Galileo antenna phase center corrections Antenna Phase Centre Offset (PCO), Variation (PCV) and Reference Point (ARP) Satellite Centre of Mass (CoM) and Attitude (user direction) Benefit Tie GNSS phase measurements consistently to the spacecraft CoM Especially relevant for GNSS-based realization of terrestrial scale, independent of SLR/VLBI Galileo is the first GNSS disclosing the full range of metadata for each antenna and carrier frequency Radial antenna offsets for other GNSS become accessible without the need to adopt any external scale Status GSAT01 released during Initial Service Declaration (Dec-2016) GSAT02 under release process. Recommendation ANTEX format update to handle COM / ARP Location https://www.gsc-europa.eu/support-to-developers/galileo-iov-satellite-metadata#2 https://ilrs.cddis.eosdis.nasa.gov/missions/satellite_missions/current_missions/ga01_com.html ESA UNCLASSIFIED - For Official Use ESA 05/07/2017 Slide 19
THANKS for your attention ESA UNCLASSIFIED - For Official Use ESA 05/07/2017 Slide 20