optomechanical design and analysis for nanosatellite laser
TRANSCRIPT
Optomechanical Design and Analysis for Nanosatellite Laser Communications
L. Yenchesky, O. Cierny, P. Grenfell, W. Kammerer, P. Periera, T. Sevigny, K. Cahoy
Space Telecommunications, Astronomy, and Radiation Lab (STAR Lab)
MIT Department of Aeronautics and Astronautics
Overview
1. Introduction
2. Optical Design
3. Structural Design
4. Spacecraft Thermoelastic &
Payload Thermal Model
5. Summary & Future Work
2
Image: P. Grenfell
Introduction
3
Mission Beam Divergence Angle Link Type Ref.
Aerocube 7 A, B, CA: 1260 arcsec (6.11 mrad)B: 180 arcsec (0.873 mrad)C: 540 arcsec (2.61 mrad)
LEO to Ground [1]
CLICK-A 268 arcsec (1.3 mrad) LEO to Ground [2]
OSIRIS 41.2 arcsec (200 urad) LEO to Ground [3]
CLICK-B/C 14.6 arcsec (70.8 urad) LEO to LEO or Ground [4]
LLCD 3 arcsec (15 urad) Lunar to Ground [5]
TerraSAR-X 1.9 arcsec (9 urad) LEO to LEO [6]
SPOT-4 0.74 arcsec (3.6 urad) LEO to GEO [7]
CLICK B/C (LEO Lasercom Crosslink)
4
Communications 20 Mbps or higher, Full-duplex, PPM,1537 / 1565 nm, 14.6” divergence, 200 mW
Crosslink Range 25 km - 580 km (extended goal 10-855 km)
Ranging (no GPS) 0.5 m (extended goal 5 cm w. GPS)
Downlink LEO to a COTS 30 cm diameter telescope (MIT PorTeL)
Size, Power 147 mm x 96 mm x 96 mm,Volume < 2U, Mass < 2 kg, Peak power < 40 W
Beacon 976 nm, 0.75 degree divergence, 500 mW
Attitude ControlBus and payload exchange ADCS information/commands to point coarsely at the other spacecraft.
Fine Steering±1 degree throw MEMS fast steering mirror from Mirrorcle Technologies rejects remaining fine pointing error.
NASA AmesMIT PI: Kerri CahoyUF Co-I: John Conklin
Image: L. Yenchesky
Overview
1. Introduction
2. Optical Design
3. Structural Design
4. Spacecraft Thermoelastic &
Payload Thermal Model
5. Summary & Future Work
5
Image: L. Yenchesky
Optical Paths
6
115 mm Image: L. Yenchesky
Slide: O. Cierny, P. serra [4]
Beacon250 mW, 976
nm22 mrad 1/e2
Transmit200 mW, 1537 nm
120 µrad 1/e2
Receive1563 nm20 mm
aperture
Optical Analysis
7
• Optimization of optics in Zemax → MATLAB– Beacon PSF sizing on quadcell to determine
optimal tracking precision• Tolerancing analysis to determine machining
precision & where kinematic mounts are necessary
Transmit & APD Receive Analysis (1537/1565 nm)
Quadcell Receive Analysis (976 nm)
Beacon PSF on Quadcell (zoom-in)
128 um
Images: O. Cierny
16 um
Optical Mounting
8Images: L. Yenchesky
• Tip/Tilt Kinematic Mounts for an adjustment resolution better than +/- 30 arcsec for the beacon laser and +/- 3 arcsec for the transmit laser.
• X & Y Decenter Kinematic Mounts for an adjustment resolution better than +/- 15 um for both sensors.
Overview
1. Introduction
2. Optical Design
3. Structural Design
4. Spacecraft Thermoelastic &
Payload Thermal Model
5. Summary & Future Work
9
Image: L. Yenchesky
BC Payload Design
10
Image: T. SevignyImage: L. Yenchesky
Slide: O. Cierny [4]
CSA
C
Structural Analysis
Static Analysis for 30 G Loading
Static Direction
Margin of Safety (MOS)
X 21
Y 44
Z 16
MOS > 0 Requirement
Satisfied
11
Images: L. Yenchesky
Typical launch static structural loading range:
4.55 - 11 G [9-11]
Structural Analysis
Resonant Freq Analysis
Mode No. Freq (Hz)
1 888
2 955
3 1023
4 1030
5 1089Typical launch random structural
vibration range: 100 - 250 Hz [9-11]
12
Image: L. Yenchesky
Modes 1 & 2
Modes 3 & 4
Mode 5
Factor of safety > 3
Fastener Analysis
13
Fastener Analysis [12]
Mounted Element
Mass (g)
Joint Separation
MOS
Pure Shear MOS
Pure Tensile
MOS
Payload 1500 16 27 14
Bench Assm. 471 19 40 21
Camera 179 60 103 55
TelescopeAssm.
18 251 467 245
Quadcell Assm.
15 511 868 466
MOS > 0 Requirement Satisfied
Image: L. Yenchesky
Overview
1. Introduction
2. Optical Design
3. Structural Design
4. Spacecraft Thermoelastic &
Payload Thermal Model
5. Summary & Future Work
14
Image: L. Yenchesky
Spacecraft Thermoelastic Analysis
15
Images: L. Yenchesky, W. Kammerer
• Assessment of pointing error due to thermoelastic expansion of S/C body• Relative alignment between S/C star tracker and CLICK apertures• 300 arcsec thermoelastic aperture
misalignment requirement to meet.• Thermal Desktop → FEMAP → MATLAB
Spacecraft Thermoelastic Analysis
16
Images: L. Yenchesky
99th percentile estimates (9 arcsec) well within allocations (300 arcsec)
Future Work - Payload Thermal Model
• Primarily passive bench thermal design– reduction of thermal gradients– temperature stability on optical bench
• 2 Cases– Standby mode– Full-duplex transmit mode
• Thermal and thermoelastic analysis results are in-progress.
17
Image: W. Kammerer
Payload Thermal Desktop Model
18
● Compact < 1.5U lasercom terminal design for 70.1 urad narrow beam laser communications crosslinks and downlinks > 20 Mbps
● Precision kinematic optical design allows optical system calibration on the ground.
● Structural analysis of payload structure and fasteners shows that the current design meets MOS & modal requirements.
● Thermoelastic analysis of 3U structure yields up to 9 arcsec of aperture misalignment, well within the 300 arcsec allocation.
Future work:
● Finalized Thermal & Thermoelastic analysis of payload structure.
● Engineering model assembly & integration.
● Engineering model vibrations and thermal vacuum testing.
Summary & Future Work
4/24/2018
Questions
19
4/24/2018 20
[1] Janson, S., Welle, R., Rose, T., Rowen, D., Hardy, B., Dolphus, R., … Hinkley, D. (2015). The NASA Optical Communications and Sensor Demonstration Program : Initial Flight Results. 29th Annual AIAA/USU Conference on Small Satellites.
[2] Payne, C., Aguilar, A., Barnes, D., Diez, R., Kusters, J., Grenfell, P., … Cahoy, K. (2018). Integration and Testing of the Nanosatellite Optical Downlink Experiment. 32nd Annual AIAA/USU Conference on Small Satellites.
[3] Schmidt, C., Brechtelsbauer, M., & Rein, F. (2014). OSIRIS Payload for DLR’s BiROS Satellite. Conference on Space Optical Systems. Retrieved from http://elib.dlr.de/89346/
[4] Serra P., Cierny O., Diez R., Grenfell, P., Gunnison, G., Kammerer, W., Kusters, J., … , Stupl, J. (2019). Optical Communications Crosslink Payload Prototype Development for the Cubesat Laser Infrared CrosslinK (CLICK) Mission. 33rd Annual AIAA/USU Conference on Small Satellites.
[5] Khatri, F. I., Robinson, B. S., Semprucci, M. D., & Boroson, D. M. (2015). Lunar Laser Communication Demonstration operations architecture,. Acta Astronautica, 111, 77–83. https://doi.org/10.1016/j.actaastro.2015.01.023
[6] Buckreuss, S., Balzer, W., Muhlbauer, P., Werninghaus, R., & Pitz, W. (2003). The terraSAR-X satellite project. IGARSS 2003. 2003 IEEE International Geoscience and Remote Sensing Symposium. Proceedings (IEEE Cat. No.03CH37477), 5(C), 3096–3098. https://doi.org/10.1109/IGARSS.2003.1294694
[7] Perez, E., Bailly, M., & Pairot, J. M. (1989). Pointing Acquisition And Tracking System For Silex Inter Satellite Optical Link. SPIE 1989 Technical Symposium on Aerospace Sensing, 1111. https://doi.org/10.1117/12.977988
[8] Grenfell P., Aguilar A., Cahoy K., Long M. (2018). Pointing, Acquisition, and Tracking for Small Satellite Laser Communications. 32nd Annual AIAA/USU Conference on Small Satellites
[9] (2015) Minotaur IV V VI User’s Guide, Release 2.2.
[10] Legier, R. (2016) Ariane 5 User’s Manual.
[11] (2013) General Environmental Verification Standard.
[12] Chambers, J. (1995) NASA Preloaded Joint Analysis Methodology for Space Flight Systems Memorandum.
References
4/24/2018
Backup
21
Motivation
22
• To enable new distributed & coordinated sensing missions
• There is a need for:– Mbps-rate full-duplex crosslinks– Precision ranging and timing
• Goal: Development of miniaturized optical transceivers based on COTS components & compatible with CubeSat SWaP constraints
Distributed sensing
networks
CLICK Payloads
23
CLICK-A• Single 1.2 U, 800 g, <15 W payload• 200 mW avg. Tx, 1.3 mrad beam• Uplink beacon at 976 nm for PAT
– Up to ±3° bus pointing error rejection capability
• Rate-scalable M-ary PPM downlink– 40 Mbps with 1 m Rx telescope– 10 Mbps with 30 cm telescope
• Primary success criteria:– Validate laser transmitter– Validate fine-pointing stage– Validate optical GS– Successful >10 Mbps downlink
CLICK-B/C
• Pair of 1.5 U, ~1700 g, <25 W payloads• 200 mW avg. Tx, 70 urad divergence• 25 cm receive aperture• 500 mW beacon at 976 nm for PAT• Full-duplex PPM crosslinks 1537/1565 nm
– 50 Mbps, 4-PPM, <450 km– 25 Mbps, 16-PPM, <920 km
• 200 ps timing accuracy & time transfer
• Primary success criteria:– >20 Mbps full-duplex @ 580 km– <0.5 m ranging w/o GPS @ 580 km
AB C
1537 nm Transmit
1565 nm Receive
1550
nm
Dow
nlin
k
Concept of Operations
24
PAT Staging & Budget
25
Credit: M. Long
Image: P. Grenfell
Payload Architecture
26
Optical Path
27
Configuration
28
MEMS FSM
APD
Telescope
Camera
Beacon
Quadcell DichroicsTx Laser
29
Zemax® Optical Raytracing
Optical Modeling
S/C Thermoelastic
30
3U Spacecraft Thermal Model
Optical Ground Terminal
31
• MIT-developed Portable Telescope for Lasercom (PorTeL)
• Based on ⌀28 cm Celestron CPC1100
• Fitted with a custom backend & star camera
• Rapid setup and pointing calibration based on star camera quaternion solution (<15 min)
Credit: K. Riesing [2,3]
Image: T. Sevigny
CLICK B/C Coarse PAT
32
Images: P. Grenfell
CLICK B/C Fine Tracking Flow
33
Image: P. Serra
Optomechanical Design Elements
34
assembly alignment & calibration
thermoelastic effects
structural modes & static loading
fastener analysis
Images: L. Yenchesky, D. Barnes
Optomechanical Engineering
35
• Sub-field of optical engineering where optics are integrated into a mechanical structure to form an instrument
• Requires integrated models for optical systems performance prediction
• Often includes all phases ofmission developing, including I&T
115 mm
Image: L. Yenchesky