Orbit Evolution of the Swarm Mission Detlef Sieg

Transcription

1 Orbit Evolution of the Swarm Mission Detlef Sieg

2 Content Orbit history absolute Aerodynamic scale factors from orbit determination Altitude history and prediction RAAN/LTAN (orbit plane rotation) Orbital plane differences DLTAN lower pair wrt upper Swarm-B DRAAN/DInclination in between lower pair satellites In-plane separation, lower pair satellites Relative drag Semi major axis / along track separation Eccentricity/altitude difference Fuel consumption Outlook (constellation)

3 Orbit history absolute, drag Based on fixed Swarm cross section area of 1.1 m 2 and NRLMSISE-00 atmosphere model. Value of 3.0 has been used for predictions. Average value during past six months was 2.6

4 Orbit history absolute, altitude Up to now strongest decay during max of current solar cycle

5 Osculating semi major axis at ascending node [km] Orbit history absolute, altitude lower pair Orbit evolution: Altitude 6850 Lower pair predicted versus actual height evolution Predictions done in: / / All predictions have been done with an aerodynamic drag force scale factor of 3.0 and 5 th, 50 th, 95 th percentile for values of solar activity indices used by NRLMSISE-00 drag model 05/ / Observed

6 Orbit history absolute, altitude Orbit evolution: Altitude Swarm predicted height evolution from September 2016 Decay rate 400km Without orbit manoeuvres the re-entry of lower pair is between 2022 and 2028 (2030) 300km altitude

7 Orbit history absolute, orbital plane. W: ~10 deg / month

8 Orbit history absolute, orbital plane ~9 months

9 Lower pair, orbital plane wrt Swarm-B LTAN difference of higher Swarm-B increases 1.5h per year. Current value is 4.2h. End of 2021 DLTAN12h could be reached where all satellites are in same plane but Swarm-B orbits in opposite direction.

10 Lower pair, orbital plane differences observed Evolution of RAAN difference mainly due to tiny inclination difference

11 Lower pair, orbital plane differences 0 A-C inclination difference has been remaining close to zero <= deg

12 Lower pair, in-plane separation Mid November 2015: 1.8% 0.75% Jun/Jul/Aug 2014: 0.5% 0.75% 0.4% For manoeuvre planning ESOC FD uses currently an aerodynamic scale factor of Swarm-C being 0.4% higher than the Swarm-A value 3.0.

13 Lower pair, in-plane separation Daily average pointing for October 2015 as calculated by FD ATT Yaw Pitch Roll 0.07 deg Swarm-C had systematically a slightly higher depointing than Swarm-A deg increases front area by 7.5m 2 (Sin(0.47)-Sin(0.40))=0.09 m m m 2 which is 0.8%.

14 Lower pair, in-plane separation So far Swarm-A performed 10 formation maintenance manoeuvres. And Swarm-C one. Only two manoeuvres since last IOP: 10+11

15 Lower pair, in-plane separation

16 Lower pair, in-plane separation One manoeuvre was dedicated to eccentricity control to get < 1e-5 Last two routine manoeuvres were used to reduce it further.

17 Lower pair, in-plane separation Altitude difference at orbit crossing points. Has to be kept small for collision avoidance in case of safemode.

18 Fuel history 38kg spent during orbit acquisition phase

19 Fuel history 30g CAM 70g for slews to 40 deg yaw ~43g for ACC scale factor calibration 152g for 101g eccentricity CAM control 87g CAM CAM= collision avoidance manoeuvre Yearly consumption < 1kg

20 Outlook constellation Plenary session to discuss future Swarm constellation options took place during 6 th Data Quality Workshop in Sep Scientists to perform simulations till Fourth Swarm Science Meeting in March 2017 in Banff (Canada) 60 km / 30 kg of fuel 64 km /32 kg of fuel Raise orbits, extend lifetime to solar cycle min 2030 Go lower (350 km), timing wrt solar cycle Maintain A/C at certain low altitude Formations with A/C orbit planes close Let B orbital plane drift, reach 12h Stay longer around LTAN 6h

21 Thank you for your attention