Microsatellite Constellation for Earth Observation in the Thermal Infrared Region

Transcription

1 Microsatellite Constellation for Earth Observation in the Thermal Infrared Region Federico Bacci di Capaci Nicola Melega, Alessandro Tambini, Valentino Fabbri, Davide Cinarelli Observation

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 2

3 Introduction AS-50 Platform 3

4 Requirements Mission Statement: Design a microsatellite constellation for EO applications reducing the modifications to the current AS-50 platform and the overall mission cost Mission requirements: Innovative concept Commercial interest Single launch Adaptation of AS-50 platform Satellite mass < 100 kg (AS-50x2) Max size 440x440x820 mm 3 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: 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 4

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 5

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 6

7 Constellation Features Example of observation capabilities: Forlì, Italy (44.2 N) 109 obs. in 121 days Widely spread observation times 7

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 km 8

9 System Design Drivers (1) Operation ΔV [m/ s] Deployment Drag compensation Margin 20% Residual 2% 5.98 TOTAL ΔV Requirement Propulsion system: Monopropellant, non-toxic, low-cost Hydrogen Peroxide I sp ~120 s Required volume: dm 3 Tank issue: A large spherical tank would not allow for proper structural design of the Payload Bay (~300x300x300 mm 3 ) Use of 4 COTS cylindrical tanks (ATK) Increase of platform size: 350x350x650 mm 3 400x400x730 mm 3 9

10 System Design Drivers (2) Power generation Nadir-pointing attitude profile (Nominal Mode) Variable solar vector position System simplicity Analogy with AS-50 platform Body-mounted configuration: AOP: W (depending on LTAN) Battery Charging Mode (Sun-pointing) 10

11 System Design Drivers (3) Payload Sensor: Uncooled microbolometer 1024x768 px, 17µm pitch Optics: EFL=162 mm D = 118 mm Swath = km Duty cycle: PL Power ~ 5.8 W Increases RF power Reduces batteries life Average Consumption: W (with margins) 11

12 Subsystems (1) Telecommunications GS selection within Estrack network Perth (Australia) + Santiago (Chile) Access for 81% of orbits (10 deg elevation) Average access time 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 12

13 Subsystems (2) AOCS Increased agility and accuracy Main sensors: Star Trackers GPS Receiver Main actuators: 3+1 RWs H 2 O 2 µthrusters EPS BM Solar Panels: x60 mm 2 Ga-As cells per panel Li-Ion Batteries: Same as current AS-50 6 packages, 6 batteries each Capacity 340 Wh 13

14 Mass Budget AOCS TELECOMMUNICATIONS 4.38 Reaction Wheels S-Band RTX Star Trackers S-band RTX Antenna Magnetorquers HPA Magnetometers LNA GPS Receiver X-band TX GPS Antenna X-band Antenna Prop. System X-band HPA Prop. Electronics Cabling Propellant Tanks Propellant STRUCTURE All values include 20% margin Bus Module Payload Module Lateral Panels POWER 4.56 Battery Packs PDU PMB OBDH 0.53 OBDH PAYLOAD 3.96 Sensor Baffle Optics Electronics TOTAL MASS: kg 14

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 mm 3 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! 15

16 Contacts Federico Bacci di Capaci Mission Analyst SITAEL S.p.A. Premises Via Filippo Guarini, Forlì (FC) ITALY Tel: Headquarters Via San Sabino, Mola di Bari (BA) ITALY Tel: Fax: