P. Sarti, C. Abbondanza, S. Montaguti, M. Negusini, L. Vittuari 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 Fixed axis Moving axis O Telescope Invariant Point Antenna Reference Point (ARP)
Reference point: electronic definition frequency dependent elevation dependent
Reference point: stochastic definition RP is realized using observations performed by space techniques 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” sphere i-th vertical circle i-th vertical plane i-th “vertical” sphere
Medicina: visione globale della rete locale N 20m
Medicina: posizione degli strumenti geodetici spaziali GPS VLBI
Medicina: dettaglio dei segnali rilevati sul radiotelescopio
P1 (mm) P3 G7 GPS ARP VLBI IP 2002-2001 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 2003-2001 -6.32 6.45 -3.51 9.69 4.73 -0.32 0.68 -4.32 -0.77 0.89 -3.14 0.84 1.83 -0.42 7.94 7.06 6.54 5.86 9.73
(U IPE -U IPF) 1 cm U IPF=17.6933±0.0007 (m) U IP0=17.7003±0.0008 (m) U IPF=17.6933±0.0007 (m) U IPE=17.7030±0.0003 (m) (U IPE -U IPF) 1 cm
Focal length Receiver Vertex e Df O
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