Tecniche terrestri di rilievo applicate alle antenne VLBI
Tecniche terrestri di rilievo applicate alle antenne VLBI per lo studio delle deformazioni gravitazionali P. Sarti, C. Abbondanza, S. Montaguti, M. Negusini, L. Vittuari
Summary • Space geodetic instrument reference point: – Definition (conventional, stochastic, electronic) – Stability • Local ties and eccentricity vectors • Investigation on gravitational deformations affecting Medicina’s VLBI telescope: – Terrestrial measurements: • Topography • Laser scanning – Finite Element Model • An elevation-dependent signal path correction model: – Combination of deformations – Signal path variation
Reference point: conventional definition Telescope Invariant Point O Moving axis Antenna Reference Point (ARP) Fixed axis
Reference point: electronic definition i. frequency dependent ii. elevation dependent
Reference point: stochastic definition a. RP is realized using observations performed by space techniques b. RP is realized with terrestrial surveying − − − Direct method Indirect method Hybrid method
GPS survey approach
j-th horizontal circle j-th horizontal plane j-th “horizontal” sphere
i-th vertical circle i-th vertical plane i-th “vertical” sphere
Medicina: visione globale della rete locale N 20 m
VLBI GPS Medicina: posizione degli strumenti geodetici spaziali
Medicina: dettaglio dei segnali rilevati sul radiotelescopio
P 1 (mm) P 3 (mm) G 7 (mm) GPS ARP (mm) VLBI IP (mm) X -1. 87 3. 17 -1. 51 2. 08 Y 1. 57 -2. 85 0. 01 -0. 81 2. 09 Z 0. 57 -2. 38 -0. 53 2. 48 -0. 13 mod 2. 51 4. 16 3. 22 3. 01 2. 95 X -6. 32 6. 45 -3. 51 9. 69 Y 4. 73 -0. 32 0. 68 -4. 32 -0. 77 Z 0. 89 -3. 14 0. 84 1. 83 -0. 42 mod 7. 94 7. 06 6. 54 5. 86 9. 73 2002 -2001 2003 -2001
U IPF=17. 6933± 0. 0007 (m) U IP 0=17. 7003± 0. 0008 (m) U IPE=17. 7030± 0. 0003 (m) (U IPE -U IPF) 1 cm
Focal length Receiver Vertex Df O e
Clark and Thomsen 1988
Elevation 90 deg
Elevation 75 deg
Elevation 60 deg
Elevation 45 deg
Elevation 30 deg
Elevation 15 deg
g
g
g
Displacement of the receiver g
Displacement of the receiver g
Displacement of the receiver g
Displacement of the receiver g
g
Displacement of the vertex g
- Slides: 50