in#co&opera+on#with# Space-Based Polar Remote Sensing... Slide 2 Introduction Value of space-based...
Transcript of in#co&opera+on#with# Space-Based Polar Remote Sensing... Slide 2 Introduction Value of space-based...
www.strath.ac.uk/mae Slide 1
Space-Based Polar Remote Sensing
Malcolm Macdonald working with Pamela C Anderson, Carl Warren & Ben Dobke
12 October 2012 [email protected] www.strath.ac.uk/mae
in co-‐opera+on with
View of Earth at 1200hrs UTC, 12 October 2012
www.strath.ac.uk/mae Slide 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,
12 October 2012 [email protected] www.strath.ac.uk/mae Slide 2
www.strath.ac.uk/mae Slide 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…
12 October 2012 [email protected] www.strath.ac.uk/mae Slide 3
www.strath.ac.uk/mae Slide 4
• Spacecraft monitor the Earth from two basic orbital positions, – near-polar LEOs of about 600 – 800 km altitude giving detail, – GEOs at ~36 000 km above the Earth giving context
12 October 2012
www.strath.ac.uk/mae Slide 5
GEO platforms Suffer rapidly decreasing horizontal resolution with increasing latitude; many products not available north of the central belt
12 October 2012 [email protected] www.strath.ac.uk/mae
Image Credit: E
UM
ETS
AT
Slide 5
www.strath.ac.uk/mae Slide 6
Atmospheric Motion Vectors
Hourly AMVs generated using composite images • A ‘ring’ of missing
observations exists – from <50° to >70°
12 October 2012 [email protected]
GEO
LEO
GAP
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, 22-‐26-‐February 2010
www.strath.ac.uk/mae Slide 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 <45 000 km altitude
12 October 2012 [email protected]
www.strath.ac.uk/mae Slide 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.
12 October 2012 [email protected]
www.strath.ac.uk/mae Slide 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!
12 October 2012 [email protected]
Image Credit: ESA
Image Credit: B
BC
www.strath.ac.uk/mae Slide 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
12 October 2012 [email protected]
AcceleraBon required assuming conBnuous acceleraBon.
www.strath.ac.uk/mae Slide 11
Molniya v’s Taranis Molniya Taranis Inclination 63.4° 90° Perigee Altitude 300 km 300 km Orbit period 12 hours 12 hours Minimum ZOA at 55° latitude at all longitudes 69° 50° Number of spacecraft required to image all longitudes from 55 – 90° latitude with OZA < 60° (composite coverage)
3 2
Number of launches required (composite coverage)
3 1
Number of spacecraft required to image all longitudes from 55 – 90° latitude with OZA < 60° (single platform coverage)
impossible 3
Number of launches required (single platform coverage) n/a 1
12 October 2012 [email protected]
www.strath.ac.uk/mae Slide 12
Mission Analysis Two 90° orbits consider, • Quantifying impact of
mitigating space environment effects
• ‘Soft’ orbit is, – 10000 x 41740 km (16-hr) – & requires 4 spacecraft
• ‘Hard’ orbit is, – 300 x 40170 km (12-hr) – & requires 3 spacecraft
12 October 2012
www.strath.ac.uk/mae Slide 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
12 October 2012
www.strath.ac.uk/mae Slide 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 October 2012 [email protected]
12-‐hr orbit shown
www.strath.ac.uk/mae Slide 15
System-Level Mass Allocations • Single platform coverage of target region
– Assuming a Soyuz launch from CSG
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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 & no thrusting in shadow region)
5 mN 80.6 mN
Specific Impulse 3500 s 4600 s Electric Propulsion Input Power 0.6 kW 4.8 kW
www.strath.ac.uk/mae Slide 16
Soyuz Payload Mass Allocation 16-hr; Single platform coverage • Payload mass
– 5-yr = 130 – 215 kg – 7.5-yr = 125 – 210 kg
12-hr; Single platform coverage • Payload mass
– 5-yr = 70 – 120 kg – 7.5-yr = 40 – 70 kg
12 October 2012 [email protected]
www.strath.ac.uk/mae Slide 17
System-Level Mass Allocations • Composite coverage of target region
– Assuming a Soyuz launch from CSG
12 October 2012 [email protected]
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 & no thrusting in shadow region)
17.3 mN 162 mN
Specific Impulse 3500 s 4400 s Electric Propulsion Input Power 0.6 kW 10 kW
www.strath.ac.uk/mae Slide 18
Soyuz Payload Mass Allocation 16-hr; Composite coverage • Payload mass
– 5-yr = 270 – 455 kg – 7.5-yr = 265 – 445 kg
12-hr; Composite coverage • Payload mass
– 5-yr = 65 – 110 kg – 7.5-yr = 20 – 35 kg
12 October 2012 [email protected]
www.strath.ac.uk/mae Slide 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
12 October 2012 [email protected]
www.strath.ac.uk/mae Slide 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
12 October 2012 [email protected]
www.strath.ac.uk/mae Slide 21
Conclusions
3 (or 4) spacecraft can provide continuous single platform observation of all longitudes at latitudes 55 – 90°
– with OZA <60°
• Only 2 spacecraft with composite images – 3 required on critical inclination orbits
12 October 2012 [email protected]
www.strath.ac.uk/mae Slide 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
12 October 2012 [email protected]
www.strath.ac.uk/mae Slide 23 12 October 2012 [email protected] Image Cred
it: SeeGlasgow
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www.strath.ac.uk/mae Slide 24 12 October 2012 [email protected] Image Cred
it: SeeGlasgow
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www.strath.ac.uk/mae Slide 25
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