Status of the ACES mission

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Pauline York
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1 Moriond Workshop, March 2003 «Gravitational Waves and Experimental Gravity» Status of the ACES mission The ACES system The ACES payload : - space clocks : PHARAO and SHM - on-board comparisons - space-ground clocks comparisons with the microwave link MWL ISS orbit determination The operations and coordination of ACES ground users Moriond Workshop Les Arcs, March

2 The ACES system PHARAO : Cold Cs atoms clock PHARAO XPLC SHM SHM : Space Hydrogen Maser FCDP : Frequency Comparison and Distribution Package FCDP XPLC : External payload computer ISS MWL space segment PDU TM TC PDU : Power distribution unit MWL : Microwave Link ASOC ASOC : ACES control and mission center MWL ground terminals Specific needs : Precise ISS orbit determination ACES payload microvibrations level Moriond Workshop Les Arcs, March

3 The ACES payload Moriond Workshop Les Arcs, March

4 ACES on ISS Launch ULF-3 end of 2006 COLUMBUS module Express Pallets ACES LOCATION Moriond Workshop Les Arcs, March

5 ACES PAYLOAD (Astrium, France and Germany) MWL ANTENNAS MWL PDU BGU XPLC PHARAO HEAT PIPES SHM PHARAO CESIUM TUBE PHARAO - OLS Volume 1 m 3 Mass 225 kg Power 400 W Moriond Workshop Les Arcs, March

6 ACES SPACE CLOCKS : PHARAO & SHM Moriond Workshop Les Arcs, March

7 ACES space clocks performance PHARAO stability better than σ y (τ) = τ -1/2 (in frequency) σ x (τ) = τ +1/2 (in time) PHARAO accuracy target : SHM stability better than PHARAO stability for mid-term PHARAO SHM 100 PHARAO SHM 12 1 day σ y (τ) day σ x (τ) [ps] , τ [s] 0, τ [s] Moriond Workshop Les Arcs, March

cavity cavity magnetic shields (4x) thermal shield external magnetic shield vacuum main

8 SHM PHYSICS PACKAGE (Neuchâtel Observatory, Switzerland) physics package cut view PTFE storage bulb collimator cavity thermal shield & c-field sapphire storage bulb microwave cavity cavity magnetic shields (4x) thermal shield external magnetic shield vacuum main structure assembly hydrogen beam assembly dissociator assembly Moriond Workshop Les Arcs, March

9 SHM DESIGN Magnetic shield hydrogen distribution RF oscillator Electronic package ion pump high voltage supply ion pump! Thermal sensitivity ( f/f per C), magnetic control ( 1 µg 0.1 nt) Moriond Workshop Les Arcs, March

PHARAO CESIUM TUBE DESIGN (SODERN, France) ATOMIC STATE PREPARATION REGION DETECTION REGION Cs RESERVOIR COOLING REGION MICROWAVE INTERROGATION

10 PHARAO CESIUM TUBE DESIGN (SODERN, France) ATOMIC STATE PREPARATION REGION DETECTION REGION Cs RESERVOIR COOLING REGION MICROWAVE INTERROGATION REGION!UHV : a few torr ION PUMP!Cavity temperature control (0.1 C), magnetic control (< 1 µg 0.1 nt) Moriond Workshop Les Arcs, March

11 PHARAO DESIGN CESIUM TUBE PHARAO COMPUTER (EREMS) ION PUMP MICROWAVE SOURCE OPTICAL LASER SOURCE Moriond Workshop Les Arcs, March

12 OPTICAL LASER SOURCE DESIGN (SODERN, France) Alignment both in air and under vacuum Redundancy of laser diodes Moriond Workshop Les Arcs, March

13 EXTENDED CAVITY LASER DESIGN (SODERN, France)! High spectral purity laser diode for laser cooling and clock signal detection ECL breadboard test Moriond Workshop Les Arcs, March

192 GHz) to avoid any degradation of PHARAO frequency stability " High

14 MICROWAVE SOURCE DESIGN (Thalès,Cemac, France)!High spectral purity microwave interrogation signal GHz) to avoid any degradation of PHARAO frequency stability " High performance quartz oscillator! stability 7. 1 s " Microwave source detail Moriond Workshop Les Arcs, March

15 PHARAO GROUND TESTING EQUIPMENT (CNES, France) Vacuum chamber for PHARAO tests Moriond Workshop Les Arcs, March

16 Clocks comparisons in space : the FCDP and the SERVO LOOPS Moriond Workshop Les Arcs, March

The FCDP and the «Servo loops» PHARAO OLS CS Resonator 9.2GHz DDS 2 100 MHz UGB FCDP XPLC MICRO CONTROLER SHM H Resonator DDS 1.

17 The FCDP and the «Servo loops» PHARAO OLS CS Resonator 9.2GHz DDS MHz UGB FCDP XPLC MICRO CONTROLER SHM H Resonator DDS 1.4 GHz 100 MHz σ y (τ) PHARAO SHM ACES clocks DDS 1 MWL Space terminal 10 MHz FCDP and servo loops breadboard 10 MHz 10 (Timetech, Kayser-Threde, Germany) τ [s] Short term servo loop : improvement of PHARAO mid-term stability Long term servo loop : correction of SHM frequency drifts! The signal delivered to the ground has the stability of the best clock and PHARAO accuracy Moriond Workshop Les Arcs, March

18 Space ground clocks comparisons with the microwave link MWL All ACES major scientific objectives rely on space ground comparisons : Short term comparisons (special relativity tests : δc/c) Long term comparisons (general relativity tests : red shift, α variation) Moriond Workshop Les Arcs, March

Clocks comparisons with MWL " Low orbit of ISS : 400 km " Period : 90 min " Mean visibility duration : 300 s Comparison sessions with ACES clocks for different ground clocks : 90

19 Clocks comparisons with MWL " Low orbit of ISS : 400 km " Period : 90 min " Mean visibility duration : 300 s Comparison sessions with ACES clocks for different ground clocks : 90 min 300 s Ground clock A Ground clock B Ground clock C Ground clock D time 1 day Non-common view comparisons Common-view comparisons Moriond Workshop Les Arcs, March

20 MWL PERFORMANCE STABILITY : 100 PHARAO SHM MWL σ x (τ) [ps] day 0, ps over 1 pass τ [s] ACCURACY : No need (time interval comparisons only) But the MWL ground terminal delays will be calibrated with an uncertainty below 100 ps Moriond Workshop Les Arcs, March

21 COMPARISON BETWEEN TWO DISTANT CLOCKS V multipath SPACE INSTRUMENT Electrical reference point ionosphere troposphere TROPOSPHERIC DELAY (temperature, humidity) IONOSPHERIC DELAY (TEC, varies as 1/f 2 ) MULTI-PATH EFFECT! 10 ns! 10 ns (distance, reflectivity of spurious reflectors) INSTRUMENTAL DELAYS (temperature, frequency and power of signals, incidence angle,.)! 100 ps/k RELATIVISTIC EFFECTS (Position and velocities of space and ground clocks ) GROUND TERMINAL! 1 st order Doppler effect! ! 2 nd order Doppler effect! Electrical reference point! Sagnac effect! ! Gravitational shift! Moriond Workshop Les Arcs, March

22 CHARACTERISTICS OF MWL (Timetech, Kayser-Threde, Germany) Two way technique in Ku band : Down 15 GHz (0.5 W) Up 13,5 GHz (4 W)! removal of troposphere, 1st order Doppler instrumental delays, ACES clock Additional S band down link (@ 2.25 GHz W)! for TEC determination Phase PN code modulation :! removal of 2π phase ambiguity Phase comparisons in space and on ground Carrier phase and code phase measurements (1 measurement / s) both in space and on the ground Data link (2 kbits/s in S-band down link)! to obtain clock comparison results in real time Earth clock 4 simultaneous ground users capability for common view comparisons Moriond Workshop Les Arcs, March

DESIGN AND REALIZATION OF MWL (Timetech,

23 DESIGN AND REALIZATION OF MWL (Timetech, Kayser-Threde, Germany) MWL space segment breadboard Phase comparator Main constraints : Multipaths Temperature sensitivity and calibration Typical MWL ground terminal Moriond Workshop Les Arcs, March

24 ORBIT DETERMINATION Moriond Workshop Les Arcs, March

25 Need of ACES payload precise orbit determination Moriond Workshop Les Arcs, March

26 ISS ALTITUDE VARIATIONS ALTITUDE VARIATION km DAYS! Determination of ACES payload orbit : orbit model using ISS GPS receivers data (position, velocity, attitude) + MWL ranging + laser ranging Moriond Workshop Les Arcs, March

27 ACES OPERATIONS Moriond Workshop Les Arcs, March

28 ACES OPERATIONS IGS ISS µ-gravity data Flight Dynamic Data UHB Master Station Instruments and equipment EM CADMOS CORE SYSTEM (SCOS) ASOC CNES Ground Software Validation Bench UTC ACES SCIENCE TEAM UHB ACES UHB Pharao UHB SHM UHB MWL UHB 2 and monitoring stations Others UHB 3 UHB 1 Moriond Workshop Les Arcs, March

29 CONCLUSIONS! SCHEDULED LAUNCH DATE : END of 2006 (mission duration > 18 months)! INSTRUMENTS ENGINEERING MODELS DELIVERED BEGINNING of 2004! DEMONSTRATION OF MWL CAPABILITY IN 2003! LARGE ACES TEAM (150 contributing people) in : Laboratories : BNM-SYRTE, ENS/LKB, Neuchâtel Observatory Industrial companies : Astrium, Kayser-Threde, Timetech, Sodern, Thalès, Cemac, Erems, Contraves,.. Space Agencies : ESA, CNES! ACES IS OPEN TO ANY GROUND USER WITH OR WITHOUT AN ATOMIC CLOCK The larger the number of ground ACES users, the greater the confidence in the results! Moriond Workshop Les Arcs, March

Microwave Transponders and Links ACES MWL and beyond

Workshop on Optical Clocks Düsseldorf, 08 / 09 Mar 2007 Microwave Transponders and Links ACES MWL and beyond W. SCHÄFER 1, M.P. HESS 2, 1 TimeTech GmbH, Stuttgart, Germany Wolfgang.Schaefer@timetech.de