Microsatellite Constellation for Earth Observation in the ... · Microsatellite Constellation for...

IAA Symposium on Small Satellites for Earth Observation

Microsatellite Constellation for Earth Observation in the Thermal Infrared

Region

Federico Bacci di Capaci Nicola Melega, Alessandro Tambini, Valentino Fabbri, Davide Cinarelli

IAA Symposium on Small Satellites for Earth Observations

2

Index

1. Introduction 2. Requirements 3. Constellation Design Orbital Geometry Deployment Constellation Features

4. Platform

System Design Drivers Subsystems Mass Budget

5. Conclusive Remarks

20-24 April 2015, Berlin


3

Introduction


AS-50 Platform


4

Requirements

Mission requirements: • Innovative concept • Commercial interest • Single launch • Adaptation of AS-50 platform

– Satellite mass < 100 kg (AS-50x2) – Max size 440x440x820 mm3

• Operational life 4 years

Mission definition: • Multi-Sun-Synchronous Constellation

– Repetitive illumination conditions – Best for mid-low latitudes – Max 5 satellites in different orbital planes

• Thermal Infrared Remote Sensing: – Observations during day/night – Possible use of uncooled detectors – Several applications (water management, urban heat

islands, evapotranspiration etc...) – GSD around 60 m is the target value

Mission Statement: Design a microsatellite constellation for EO applications reducing the modifications to the current AS-50 platform and the overall mission cost



5

Orbital Geometry (1)

Multi-Sun-Synchronous Constellation Conditions: • Satellites in circular periodic orbits:

– Same radius and inclination – Equally spaced in RAAN

• Each satellite provides complete coverage of the equator in a repetitiveness period

• Each satellite observes the same area at the same local time after an integer number of repetitiveness cycles

• Different satellites observe the same area with periodic illumination conditions



6

Orbital Geometry (2) • h=572 km • i = 47.7 deg • ΔΩ=72 deg

• 121 days illumination repetitiveness period • 5x3=15 equally spaced passages over the same

Ground Track



7

Constellation Features

• Example of observation capabilities: – Forlì, Italy (44.2° N) 109 obs. in 121 days – Widely spread observation times



8

Deployment Strategy

• Drifting Parking Orbit Maneuver: – Same for all satellites – Larger semi-major axis – Slower nodal drift – No out-of-plane maneuvers

• Trade-off: ΔV vs. Deployment time • Analysis results:

– ΔV=237.3 m/s – Complete deployment in 294 days – Parking orbit altitude 1027.98 km



9

System Design Drivers (1)

ΔV Requirement


Propulsion system: • Monopropellant, non-toxic, low-cost • Hydrogen Peroxide • Isp~120 s • Required volume: 14.79 dm3

Tank issue: • A large spherical tank would not allow for proper structural design of the

‘Payload’ Bay (~300x300x300 mm3) • Use of 4 COTS cylindrical tanks (ATK) Increase of platform size: 350x350x650 mm3 400x400x730 mm3

Operation ΔV [m/ s]Deployment 237.34Drag compensation 11.96Margin 20% 49.86Residual 2% 5.98TOTAL 305.14


10


Power generation


Body-mounted configuration: AOP: 28.1 ÷ 49.1 W (depending on LTAN)

• Nadir-pointing attitude profile (Nominal Mode)

• Variable solar vector position

• System simplicity • Analogy with AS-50

platform

Battery Charging Mode (Sun-pointing)


11


Sensor: • Uncooled microbolometer • 1024x768 px, 17µm pitch Optics: • EFL=162 mm • D = 118 mm • Swath = 61.44 km


Payload Duty cycle: • PL Power ~ 5.8 W • Increases RF power • Reduces batteries life

Average Consumption: 43.64 W (with margins)


12

Subsystems (1)

Telecommunications • GS selection within Estrack network

– Perth (Australia) + Santiago (Chile) – Access for 81% of orbits (10 deg elevation) – Average access time 307.3 s

• RS data downlink in X-band – 10 Mbps with 1.86 W RF (~15 W at the S/C)

• TMTC uplink/downlink in S-band – Receiver: 4.3 W – Transmitter (rms over an orbit): 0.15 W



13

Subsystems (2)

AOCS • Increased agility and

accuracy • Main sensors:

– Star Trackers – GPS Receiver

• Main actuators: – 3+1 RWs – H2O2 µthrusters


EPS • BM Solar Panels:

– 30 120x60 mm2 Ga-As cells per panel

• Li-Ion Batteries: – Same as current AS-50 – 6 packages, 6 batteries each – Capacity 340 Wh


14

Mass Budget


TELECOMMUNICATIONS 4.38S-Band RTX 2 1.20S-band RTX Antenna 2 0.36HPA 2 0.36LNA 2 0.12X-band TX 1 0.60X-band Antenna 1 0.18X-band HPA 1 0.36Cabling - 0.72

PAYLOAD 3.96Sensor 1 0.36Baffle 1 1.50Optics 1 1.50Electronics 1 0.60

All values include 20% margin

TOTAL MASS: 93.17 kg

AOCS 44.44Reaction Wheels 4 4.32Star Trackers 2 0.84Magnetorquers 6 2.95Magnetometers 2 0.34GPS Receiver 1 0.28GPS Antenna 1 0.17Prop. System 1 5.22Prop. Electronics 1 0.32Propellant Tanks 4 6.53Propellant - 24.48 STRUCTURE 32.81

Bus Module 1 11.04Payload Module 1 10.90Lateral Panels 4 10.87

POWER 4.56Battery Packs 6 3.31PDU 1 0.50PMB 1 0.74

OBDH 0.53OBDH 2 0.53


15

Conclusive Remarks


Mission requirements: Innovative concept Commercial interest Single launch Adaptation of AS-50 platform

Satellite mass < 100 kg (AS-50x2) Max size 440x440x820 mm3

Operational life 4 years

Phase-A output: • Proven feasibility • Defined orbital geometry • Initial system budgets • Preliminary subsystem

design

Alternative solutions: • Deployable SPs • Electric Propulsion • Use of TDI Read-Out mode

THANK YOU FOR YOUR ATTENTION!


Contacts

Federico Bacci di Capaci Mission Analyst

[email protected]

SITAEL S.p.A. Premises

Via Filippo Guarini, 13 47121 Forlì (FC) – ITALY

Tel: +39 0543 25280 Headquarters

Via San Sabino, 21 70042 Mola di Bari (BA) – ITALY

Tel: +39 080 5321796 Fax: +39 080 5355048

www.sitael.com

20-24 April 2015, Berlin 16

mailto:[email protected]

mailto:[email protected]

http://www.sitael.com/

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