SwissCube Project Phase B March 8, 2007

EPFL - LMTS N. Scheidegger

Science Payload

N. Scheidegger | 8 March 2007 © 2007 EPFL | UNINE | HES-SO

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Science Payload

Science Objectives

Measure the airglow emission in the upper atmosphere at 100 km altitude to :  Demonstrate the feasibility of using airglow as a basis for a low-cost Earth Sensor  Validate the established airglow model or bring additional information about airglow dependence on → latitude → altitude → local solar time Nightglow and aurora borealis © 2007 EPFL | UNINE | HES-SO

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Science Payload

Earth Appearance at 762 nm for different Solar Local Times

Min 24:00 SLT Mean 24:00 SLT Max 24:00 SLT Min 06:00 SLT Mean 06:00 SLT Max 06:00 SLT Min 12:00 SLT Mean 12:00 SLT Max 12:00 SLT © 2007 EPFL | UNINE | HES-SO

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Science Payload

Expected airglow at 700 km altitude Airglow [photons/pixel/s] *

Min Mean Max

Zenith Limb At night At day At night At day 150 9 k 30 k 1.8 M 370 22 k 75 k 450 M 750 90 k 150 k 180 M *for an aperture of Ø4 mm and a FOV of 0.16°/pixel = minimum photon flux © 2007 EPFL | UNINE | HES-SO

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Science Payload

Driving Requirements

 Payload may be a technology demonstrator of the Earth Sensor based on airglow – – Observes the emission at 762 nm with a bandwidth of at least [10] nm Has a spatial resolution of at least [0.3] ° and a FOV of at least [20] ° – Observes the airglow with a CMOS SPAD array if possible – – Survives having its boresight directly sun pointing for a period of at least 10 hours Can perform science mission with the sun no closer than [30] ° from its boresight.

 Physical constraints – Volume: [30 x 30 x 70] mm 3 [70 x 30 x 20] mm 3 for optics and detector for mainboard – – Mass: Power: [60] g [450] mW, during [10]s for each image © 2007 EPFL | UNINE | HES-SO

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Science Payload

Science Payload Instrument Design

mainboard headboard baffle filter optical system detector © 2007 EPFL | UNINE | HES-SO

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Design Description

 Detector and control electronics – Detect photons and generate digital output which is proportional to local light intensity – Provides required power and control signal for the detector – Interfaces with CDMS and ground station  Optical system – Magnifies the image – Filters the selected airglow line – – Protects detector from sun Links the detector mechanically to the satellite bus © 2007 EPFL | UNINE | HES-SO

Science Payload

Detector

8 Performance

Array size Pixel pitch Total FOV Dynamic range Fill-factor Photon Detection Probability Dark Counts (at 25 ° C) Power consumption Detected airglow signal at limb at night Detected airglow signal at limb at day

Unit

pixels μm ° dB % % Hz mW counts/pixel/s counts/pixel/s

MT9V032

188 x 120 † 24 x 24 29.4 x 18.8

100 320 4 k – 19 k 227 k 20 45 4 k †

KAC-9619

162 x 122 † 30 x 30 † 31.6 x 23.8

110 47 27 3.5 k 170 6 k – 29 k – 2.3 M 354 k – 3.5 M * for an aperture of Ø4 mm and a total FOV of 25° for a SPAD array = current baseline design † including a Binning of 4 x 4 pixels

SPAD

128 x 128 30 x 30 25 x 25 21 k 140 15 5 25 ???

350 – 1.7 k – 209 k © 2007 EPFL | UNINE | HES-SO

Optical System: Design Parameters

Parameter

Total FOV

Unit

°

Possible Values

22 – 30

Targeted Design

↑ FOV per pixel Aperture Ø Focal Length Science Payload ° mm mm μm < 0.23

≥ 6 24 /30 ↑ ↓ ↓

Remarks (Limiting parameters)

Required FOV to guarantee limb detection with a attitude determination of 10 ° Required resolution for ES operation SNR > 3 for limb measurements Determined by aperture, pixel pitch and FOV per pixel Size of a pixel of a CMOS/SPAD Pixel Pitch ( = pitch of the microlenses for the SPAD array) For the SPAD-array: Size of the Active Spot of the pixel Mass Volume Filter Baffle

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Max. optical losses μm g mm nm mm % 6 – 9 ≤ 30 ≤ Ø 30 x 50 TBD TBD < 50% ↓ ↓ ↓ ↓ DCR < 25 Hz SwissCube mass budget SwissCube volume budget centered at 762 nm protect the detector from sun radiation no closer than [30] ° from its boresight vignetting © 2007 EPFL | UNINE | HES-SO

Optical System: Baseline Design

Parameter

Total FOV

Unit

°

Possible Values 25 Targeted Design

↑ FOV per pixel Aperture Ø Focal Length Science Payload ° mm mm μm

0.2

6 24 /30

↑ ↓ ↓

Remarks (Limiting parameters)

Required FOV to guarantee limb detection with a attitude determination of 10 ° Required resolution for ES operation SNR > 3 for limb measurements Determined by aperture, pixel pitch and FOV per pixel Size of a pixel of a CMOS/SPAD Pixel Pitch ( = pitch of the microlenses for the SPAD array) For the SPAD-array: Size of the Active Spot of the pixel Mass Volume Filter Baffle Max. optical losses

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μm g mm nm mm %

6 30 Ø 30 x 50 [10]

TBD

50%

↓ ↓ ↓ ↓ DCR < 25 Hz SwissCube mass budget SwissCube volume budget centered at 762 nm protect the detector from sun radiation no closer than [30] ° from its boresight vignetting © 2007 EPFL | UNINE | HES-SO

Science Payload

Diploma project: Design of a Telescope for the SwissCube Picosatellite

      Understanding of the science and project requirements on the payload Optical design for the payload Opto-mechanical design for the payload, including selection of material for lens and support structure Assembly of the overall payload subsystem based on the CMOS detector Testing and verification of the optical properties of the payload Documentation, preparation of end-of-phase review.

   (Electrical design for the CMOS detector control) (Establishment of hardware, data flow and cabling block diagrams for the payload subsystem, including connection with the other subsystems) (Testing and verification of the electrical, power and sensitivity performance of the detector)

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© 2007 EPFL | UNINE | HES-SO

My inputs:

Science Payload     Filter design (1.5.07) Determination of the interface with the CDMS sub-system (1.4.07) (Electrical design for the CMOS detector control) (1.5.07) (Establishment of data flow and cabling block diagrams for the payload subsystem, including connection with the other subsystems) (1.5.07)

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© 2007 EPFL | UNINE | HES-SO

Science Payload

Planned meetings and reports:

  1 x per month with the whole payload subsystem team Every week: each student reports briefly his/her last analyses and results (1 A4 page)

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© 2007 EPFL | UNINE | HES-SO

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Science Payload

Questions ?

© 2007 EPFL | UNINE | HES-SO

Science Payload

CDMS – Payload Interface

 PL microcontroller: – Guarantees a standard interface between the detector and the CDMS subsystem or commands coming from the ground station

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 CDMS subsystem: – Controls activation of the payload subsystem – Provides the parameters for the detector initialization (integration time, binning factor, DCR suppression factor,…) – Reads the science data directly form the detector – – – Does image compression if necessary Formats science data according to the science data product Stores the science data until transfer to the ground station © 2007 EPFL | UNINE | HES-SO