SwissCube Project Phase B March 8, 2007 N. Scheidegger | 8 March 2007 © 2007 EPFL | UNINE | HES-SO...

SwissCube Project Phase B

March 8, 2007

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

EPFL - LMTS

N. Scheidegger

Science Payload

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Science Payload

© 2007 EPFL | UNINE | HES-SO

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

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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



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Expected airglow at 700 km altitude

Min Mean Max

Zenith

At night 150 370 750

At day 9 k 22 k 90 k

Limb

At night 30 k 75 k 150 k

At day 1.8 M 450 M 180 M

Airglow [photons/pixel/s] *

*for an aperture of Ø4 mm and a FOV of 0.16°/pixel = minimum photon flux

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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] mm3 for optics and detector

[70 x 30 x 20] mm3 for mainboard

– Mass: [60] g

– Power: [450] mW, during [10]s for each image

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Science Payload


Science Payload Instrument Design

mainboard headboard

detectoroptical system

filter

baffle

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Science Payload


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

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Science Payload


Detector

Performance Unit MT9V032 KAC-9619 SPAD

Array size pixels 188 x 120 † 162 x 122 † 128 x 128

Pixel pitch μm 24 x 24 † 30 x 30 † 30 x 30

Total FOV ° 29.4 x 18.8 31.6 x 23.8 25 x 25

Dynamic range dB 100 110 140

Fill-factor % 20 47 15

Photon Detection Probability

% 45 27 5

Dark Counts (at 25° C) Hz 4 k 3.5 k 25

Power consumption mW 320 170 ???

Detected airglow signal at limb at night

counts/pixel/s 4 k – 19 k 6 k – 29 k 350 – 1.7 k

Detected airglow signal at limb at day

counts/pixel/s 227 k – 2.3 M 354 k – 3.5 M 21 k – 209 k

* 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

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Science Payload


Optical System: Design ParametersParameter Unit Possible

ValuesTargeted Design

Remarks (Limiting parameters)

Total FOV ° 22 – 30 ↑ Required FOV to guarantee limb detection with a attitude determination of 10°

FOV per pixel ° < 0.23 Required resolution for ES operation

Aperture Ø mm ≥ 6 ↑ SNR > 3 for limb measurements

Focal Length mm ↓ Determined by aperture, pixel pitch and FOV per pixel

Pixel Pitch ( = pitch of the microlenses for the SPAD-array)

μm 24 /30 ↓ Size of a pixel of a CMOS/SPAD

For the SPAD-array: Size of the Active Spot of the pixel

μm 6 – 9 ↓ DCR < 25 Hz

Mass g ≤ 30 SwissCube mass budget

Volume mm ≤ Ø 30 x 50

↓ SwissCube volume budget

Filter nm TBD centered at 762 nm

Baffle mm TBD ↓ protect the detector from sun radiation no closer than [30]° from its boresight

Max. optical losses % < 50% ↓ vignetting

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Science Payload


Optical System: Baseline DesignParameter Unit Possible

ValuesTargeted Design

Remarks (Limiting parameters)

Total FOV ° 25 ↑ Required FOV to guarantee limb detection with a attitude determination of 10°

FOV per pixel ° 0.2 Required resolution for ES operation

Aperture Ø mm 6 ↑ SNR > 3 for limb measurements

Focal Length mm ↓ Determined by aperture, pixel pitch and FOV per pixel

Pixel Pitch ( = pitch of the microlenses for the SPAD-array)

μm 24 /30 ↓ Size of a pixel of a CMOS/SPAD

For the SPAD-array: Size of the Active Spot of the pixel

μm 6 ↓ DCR < 25 Hz

Mass g 30 SwissCube mass budget

Volume mm Ø 30 x 50

↓ SwissCube volume budget

Filter nm [10] centered at 762 nm

Baffle mm TBD ↓ protect the detector from sun radiation no closer than [30]° from its boresight

Max. optical losses % 50% ↓ vignetting

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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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Science Payload


My inputs:

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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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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Questions ?

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PL microcontroller: – Guarantees a standard interface

between the detector and the CDMS subsystem or commands coming from the ground station

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

CDMS – Payload Interface

SwissCube Project Phase B March 8, 2007 N. Scheidegger | 8 March 2007 © 2007 EPFL | UNINE | HES-SO...

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