RØMER: Study of Stellar Oscillations and Internal Dynamics

1. Aalborg University, Department of Control Engineering

2. RØMER Aalborg University, Department of Control Engineering

3. Political Boundaries Aalborg University, Department of Control Engineering

4. Industrial Boundaries Aalborg University, Department of Control Engineering

5. Financial Boundaries Aalborg University, Department of Control Engineering

6. Key Specification • Mass: 80 kg, 100kg incl. 25% Margin. • Size: 60 x 60 x 71cm in Launch Configuration • S/C Power: 70 W avg. • Battery: 33V, 4.5Ah, Li-ion • Mission Life Time: 2 years Aalborg University, Department of Control Engineering

7. Saml. Ørsted Aalborg University, Department of Control Engineering

8. Participants • Science: • Institute of Physics and Astronomy, Aarhus University • Danish Space Research Institute, Copenhagen • Copenhagen University • Technology: • Institute of Electronic Systems, Aalborg University • Ørsted.DTU, Technical University of Denmark, Lyngby • Industry: • TERMA A/S, Lystrup • Alcatel Space Denmark, Ballerup • Copenhagen Optical Company, Copenhagen • Patria Finavitec, Tampere, Finland • Auspace, Canberra, Australia • Prime Optics, Eumundi, Australia Aalborg University, Department of Control Engineering

9. Milestones • April 1999 Kick-off of Feasibility Study of Rømer • May 2000 Funding for System Definition Phase approved • May 2000 Kick-off of System Definition Phase (SDP) • Oct. 2000 Mid-Term Review • Nov. 2000 Decision to eliminate the Ballerina PL and re-focus mission • Nov. 2000 Decision to design Rømer as a single-string mission • April 2001 System Definition Review • May 2001 Complete Report and Documentation for SDP • June 2001 Start of Detailed Design Phase • Dec. 2001 Preliminary Design Review • Dec. 2002 Satellite Critical Design Review • May 2003 Satellite Integration and Test Review • May 2004 Launch (tentatively) Aalborg University, Department of Control Engineering

10. RØMER SCIENCE OBJECTIVES Study the structure, evolution and internal dynamics of a sample of stars showing stochastically excited,solar-like oscillations. This will substantially extend the very successful helioseismic studies of the solar interior. Aalborg University, Department of Control Engineering

11. Aalborg University, Department of Control Engineering

12. Aalborg University, Department of Control Engineering

13. Aalborg University, Department of Control Engineering

14. Corresponding Observations (SOHO) • Note: • Extremely small amplitudes, of order parts per million (ppm). • Blue amplitude much larger than red amplitude. Hence also signal in (blue)/(red) ratio, to beobserved by MONS. • Background is entirely due to solar granulation. Aalborg University, Department of Control Engineering

15. Main MONS Observational Requirements • Photometric precision. Need detection limit below 1 ppm. • The instrumental noise must match, but be below, the intrinsic stellar granulation noise. • Requirement on precision demands strong defocusing. • Temporal coverage. Each primary target must be observed almost continuously for at least onemonth. • Sky coverage. Primary targets are distributed over the whole sky. • Hence choose orbit giving access to entire sky during the mission. • Mission duration. At least two years (baseline), to allow study of sufficient number of stars. • Exclusion of variable neighbours. Include MONS Field Monitor to detect and correct for faintvariable stars within telescope field of view. Aalborg University, Department of Control Engineering

16. RØMER Science Payload Characteristics The primary science instruments include: • MONS Telescope having a 32 cm aperture, equipped with a high-precision photometric CCD detector for measuring oscillations of stellar intensity and color • MONS Field Monitor for examining the field of view of the MONS Telescope for faint variable stars The secondary science instruments: • Forward- and aft-looking Star Trackers of the Attitude Control Subsystem, to be used for studying variable stars • The MONS Field Monitor MONS Telescope MONS Field Monitor Aalborg University, Department of Control Engineering

17. Aalborg University, Department of Control Engineering

18. Aalborg University, Department of Control Engineering

19. RØMER in Molniya Orbit • Largest separation from Earth (Apogee): ~40000 km • Smallest separation from Earth (Perigee): ~600 km • Angle between orbit and Equator (Inclination): 63.4° • Period: 11 hours 58 min. 02 sec. (= ½ siderial day, ideal) • 10 hours of observations outside the radiation belts. • A satellite in Molniya orbit is subjected to a large dose of radiation from high-energy protons and electrons trapped in the Earth’s radiation belts. Aalborg University, Department of Control Engineering

20. SOYUZ/FREGAT Launcher FREGAT Upper Stage FREGAT with Cluster II Satellites RØMER is foreseen to be launched with a Russian SOYUZ/FREGAT rocket in mid 2004 from Plesetsk Cosmodrome The SOYUZ rocket has been launched more than 1650 times and its reliability exceeds 97% Aalborg University, Department of Control Engineering

21. Aalborg University, Department of Control Engineering

22. Aalborg University, Department of Control Engineering

23. ACS Requirements 95% confidence numbers: Pointing Error: - P/ Y: 2 arcmin - R: 60 arcmin RMS Stability Error: - 1.2 arcmin Slew Capacity - 180 deg in 10 minutes Sun Exclusion: - 60 degrees - max 30 seconds with Sun <3 deg from MONS boresight Earth/ Moon Exclusion: - 55 degrees Aalborg University, Department of Control Engineering

24. Hardware Config and concept diagram Aalborg University, Department of Control Engineering

25. Disturbance Environment Aalborg University, Department of Control Engineering

26. ACS concept diagram Aalborg University, Department of Control Engineering

27. Aalborg University, Department of Control Engineering