1 GRS Measurement By A. Cacciani Frascati, March 21th 2006

2 Introduction GRS … one of the three classical tests of General Relativity … so far it has been tested only to the first order in m/r, THAT IS, no test for the Einstein field eqn

3 Theoretical background for gravity In general where with α, β, γ constants. Einstein puts them all = 1.

4 GRS depends only on gtt. A large mass is needed to increase the expected signal Also, it should be at rest or perfectly known relative velocity: The Sun is the only choise. To the first order, for the Sun: Δν/ν is 633 m/s Doppler equivalent, that is the speed of light. The second order adds another term smaller, that is, a signal of about 1 mm/s Doppler equivalent. Theoretical background for gravity

5 Competing instruments Masers, radio,.. They have enough stability ( claimed ) But they need to be launched in orbits around the Sun

6 Competing instruments Our instrument: the MOF It is already proven to the level of It does not need to be launched around the Sun, We are looking at the SOLAR SPECTRUM Previous measurements (not MOF) of the Solar GRS did not go better than few % (LoPresto et al )

7 MISURA DEL GRS SOLARE by: Alessandro Cacciani Runa Briguglio University of Rome LA SAPIENZA, Italy Fabrizio Massa INFN sez. Di Roma Paolo Rapex External collaborator James LoPresto Edinboro University of Pennsylvania, USA

8 A sensitive test of Fundamental Physics, especially General Relativity Previous results: Pound & al. 1960: Effetto Mossbauer Vessot & al. 1980: Maser Lo Presto 1991: GRS Snider 1971: GRS

9 How to improve? Instrumental progress such as MOF Technology Two narrow bands trasmission filter: FWHM= 50 mA, tuned on a Solar Line Intrinsic stability High efficiency (30%) Photon-shot noise limited Image detector

10 In order to reach this sensitivity, a comparison between the solar MOF signals from two satellites, one near the Earth and the other close to the Sun, will cancel all the unwanted effects, but the GRS alone. The second order signal is in the range of a mm/s (Doppler equivalent), well within the capability of our MOF. Real test of General Relativity requires time dilation effect at a second order times the first order effect. On the sun we expect a second order effect of x 636 m/s 1mm/s

11 Typical Doppler image with MOF

12 Doppler signal on the solar equator

13 Preliminary Results

14 Human ResourceActivity A.Cacciani (70%) 1 ) General Supervisor 2) External contacts 3) Cell fabrication a) Lab set up b) Fabrication c) Test 4) Observations F. Massa (70%) 5) Data Acquisition Software Developm. a) Design b) Test 6) Observations R. Briguglio (70%) 7 ) Instrument set up, test and maintenance 8) Observations P. Rapex (50%) 9 ) Data reduction Software a) Analysis b) Test and implementations c) Final results production 10) Electronic design support a) Cell heaters b) CCD synchronization