Space-Based Polar Remote Sensing

Transcription

1 in co- opera+on with Space-Based Polar Remote Sensing Malcolm Macdonald working with Pamela C Anderson, Carl Warren & Ben Dobke 12 October 2012 View of Earth at 1200hrs UTC, 12 Slide October

2 Introduction Value of space-based remote sensing is widely accepted, yet polar remote sensing remains limited Engineering concept to address polar remote sensing data deficit, Slide 2

3 An example, ECMWF quantified the value of space-based observations by comparing, Medium-range forecasts using conventional data only, & Medium-range forecasts including space-based observations Found it necessary to add AMVs to conventional-data to get a basic forecast Slide 3

4 Spacecraft monitor the Earth from two basic orbital positions, near-polar LEOs of about km altitude giving detail, GEOs at ~ km above the Earth giving context Slide 4

5 Image Credit: EUMETSAT GEO platforms Suffer rapidly decreasing horizontal resolution with increasing latitude; many products not available north of the central belt 12 October 2012 Slide 5

6 Atmospheric Motion Vectors Hourly AMVs generated using composite images GEO A ring of missing observations exists GAP LEO from <50 to >70 Lazzara, M.A., et al., "High La+tude Atmospheric Mo+on Vectors: Applica+on of Antarc+c and Arc+c Composite Satellite Imagery", 10th Interna+onal Winds Workshop Tokyo, Japan, February October 2012 Slide 6

7 Mission Requirements GEO products break-down at ~55 latitude at an observation zenith angle (OZA) of ~60. Req.; Observation of all longitudes at latitudes 55 90, with OZA <60 To maximise analogy to GEO should avoid composite images, also minimises data latency, And, Req.; Maintain apogee < km altitude Slide 7

8 Молния Observations from a Molniya orbit are possible, From GEO the ZOA at 55 latitude is 63 On a Molniya orbit the minimum ZOA to all longitudes is 69 i.e. A single platform cannot provide hemispheric-like observations Polar observations would remain dependent on composite images Three spacecraft required to provide continuous observation to all longitudes at latitudes 55 90, with OZA <60 with composite images. Requires three launches October 2012 Slide 8

9 Molniya orbit inclination results from the shape of the Earth If Earth were a different shape the critical inclination would be different So, lets change the shape of the Earth! Image Credit: BBC Image Credit: ESA Slide 9

10 Taranis Orbit Use low-thrust propulsion to modify the geopotential perturbations i.e.how the spacecraft feels the gravity of Earth Thus re-define the critical inclination as a function of the thrust magnitude Molniya means lightning, while Taranis is the Celtic God of Thunder AcceleraBon required assuming conbnuous accelerabon. Slide 10

11 Molniya v s Taranis Molniya Taranis Inclination Perigee Altitude 300 km 300 km Orbit period 12 hours 12 hours Minimum ZOA at 55 latitude at all longitudes Number of spacecraft required to image all longitudes from latitude with OZA < 60 (composite coverage) Number of launches required 3 1 (composite coverage) Number of spacecraft required to image all longitudes from impossible latitude with OZA < 60 (single platform coverage) Number of launches required (single platform coverage) n/a 1 Slide 11

12 Mission Analysis Two 90 orbits consider, Quantifying impact of mitigating space environment effects Soft orbit is, x km (16-hr) & requires 4 spacecraft Hard orbit is, 300 x km (12-hr) & requires 3 spacecraft Slide 12

13 Mission Analysis Two 90 orbits consider, Both require space qualified parts, with neither requiring Rad-hard 12-hr orbit is hence likely to offer global minimum cost mission But, accepting composite images requires only 2 spacecraft on either orbit Slide 13

14 System Analysis Thrust arcs used to optimise design Significant reduction in required thruster life-time No thruster on nadir face Thrusters off when instruments on Avoids contamination concerns Provides power rich environment for instruments Note, apogee coast length varies by architecture option 12- hr orbit shown 12 October 2012 Slide 14

15 System-Level Mass Allocations Single platform coverage of target region Assuming a Soyuz launch from CSG 16-hr 12-hr Estimated Soyuz Launch Mass Capability 2442 kg 2983 kg Available Launch Mass with 20 % margin 1954 kg 2386 kg Total Wet Mass Allocation per Spacecraft 488 kg 795 kg Thrust Magnitude per R & T direction (minimum BoL coast arc about apogee 5 mn 80.6 mn & no thrusting in shadow region) Specific Impulse 3500 s 4600 s Electric Propulsion Input Power 0.6 kw 4.8 kw Slide 15

16 Soyuz Payload Mass Allocation 16-hr; Single platform coverage Payload mass 5-yr = kg 7.5-yr = kg 12-hr; Single platform coverage Payload mass 5-yr = kg 7.5-yr = kg Slide 16

17 System-Level Mass Allocations Composite coverage of target region Assuming a Soyuz launch from CSG 16-hr 12-hr Estimated Soyuz Launch Mass Capability 2442 kg 2983 kg Available Launch Mass with 20 % margin 1954 kg 2386 kg Total Wet Mass Allocation per Spacecraft 977 kg 1193 kg Thrust Magnitude per R & T direction (minimum BoL coast arc about apogee 17.3 mn 162 mn & no thrusting in shadow region) Specific Impulse 3500 s 4400 s Electric Propulsion Input Power 0.6 kw 10 kw Slide 17

18 Soyuz Payload Mass Allocation 16-hr; Composite coverage Payload mass 5-yr = kg 7.5-yr = kg 12-hr; Composite coverage Payload mass 5-yr = kg 7.5-yr = kg Slide 18

19 Soyuz Payload Mass Allocation Counterproductive to increasing spacecraft mass on 12-hr orbit Payload 100 kg drives architecture to 16-hr orbit Payload 220 kg single platform coverage in 16-hr orbit would require multiple launches Or a larger launch vehicle Payload 450 kg single platform coverage in 16-hr orbit would require larger launch vehicle Slide 19

20 Potential Payload Principle payload of a VIS & IR imager to monitor high latitude phenomena with sufficient temporal resolution related to, winds, clouds, volcanic ash plumes, sea ice, vegetation properties, snow cover, etc MSG s main payload is SEVIRI 12 spectral channels; 4 visible/nir & 8 IR 260 kg; 150 W; 3.26 Mbit/s & 7-yr nominal mission life Assuming a Soyuz launch is, aggressively compatible with single launch & platform coverage comfortably compatible with single launch composite coverage Slide 20

21 Conclusions 3 (or 4) spacecraft can provide continuous single platform observation of all longitudes at latitudes with OZA <60 Only 2 spacecraft with composite images 3 required on critical inclination orbits Slide 21

22 Conclusions Payload mass traded against mission duration, launch vehicle selection and requirement for composite images Single platform coverage from single Soyuz launch limits payload to 220 kg Challenging mass constraints for multispectral imager Composite coverage from single Soyuz launch limits payload 450 kg More than sufficient mass for multispectral imager Single platform coverage with two Soyuz launches or single larger launcher All technology appears to already at TRL 6 or above All major technology available within the UK and in areas of UK leadership Slide 22

23 Image Credit: SeeGlasgow 12 October 2012 Slide 23

24 Image Credit: SeeGlasgow 12 October 2012 Slide 24

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