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LYRA Instrument and Data Manager

Software Requirements Analysis

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Agenda

• Concept description• LIM requirements presentation (SBI)• LDM requirements presentation (SBI)• Interface issues • Open questions

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PROBA 2 orbit

• Sun synchronous• LTAN: 6:00• See emails F.Teston for details

eclipse duration

00/01/00 0:00

18/07/00 0:00

03/02/01 0:00

22/08/01 0:00

10/03/02 0:00

26/09/02 0:00

14/04/03 0:00

10/10/06 0:00 28/04/07 0:00 14/11/07 0:00 01/06/08 0:00 18/12/08 0:00 06/07/09 0:00

date

tim

e [s

]

•Eclipses: • approximately 3 months eclipse season• rest of the year: no eclipses• maximum eclipse duration approx. 1100 sec.

Concept description

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PROBA 2 Pointing

1. Frames definitions

Sun frame (Xsun, Ysun, Zsun)Xsun is spacecraft-sun axis ( = unit(Rsun – Rsc) where Rsun is the

apparent sun vector from the Earth (Sun ephemeris) and Rsc is the spacecraft position vector. If S/C position is unknown onboard, Rsc is set to zero.

Ysun is perpendicular to Xsun, in the plane defined by Xsun and the normal to the ecliptic plane, pointing towards the northern hemisphere.

Concept description

Earth Sun

Rsc

Rsun

Xsun

Ysun

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S/C Fixed Body Frame

Concept description

Mechanical frame (Xmech, Ymech, Zmech)... With respect to S/C

Payload frame (Xpl, Ypl, Zpl)...With respect to SWAP

Spacecraft fixed body frame (Xbof, Ybof, Zbof) ... Related to Payload frame, but origin in S/C COG. Reference frame for spacecraft attitude control.

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PROBA 2 Pointing

2. Pointing in observation mode

 four (baseline, up to 8 possible) large-angle rotations of 90° (or 360° / number of rotations) attitudes are commanded over one orbit in order to avoid blinding of the star trackers; For the rest of presentation: baseline number of rotations assumed) the timing of the manoeuvres is such that the exclusion angles from the star trackers towards the earth are maximised; (performed on board -> cont. variation) the 90° manoeuvres will take a few minutes and will be centred around these optimal switching times; the time until the next rotation is continuously provided; paving rotations are defined in the original sun frame.

Illuminated face ofthe Earth

left

left

left

left

Concept description

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PROBA 2 Pointing

2. Pointing in observation mode

The observation mode is commanded as follows:• the large rotation is commanded as a quaternion in the SUN frame:

[q1cmd, 0, 0, q4cmd];• the commanded large angle rotations will be taken from a list (of maximum 8) quaternions, configured by the ground;• the index of the currently used large angle rotation will continuously be provided;• the paving rotation is commanded as a quaternion in the SUN frame:

[0, q2paving, q3 paving, q4 paving]

Paving rotation around YSUN and ZSUN

Large-angle rotation around XSUN

SUN

SUN*

REF

Concept description

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Concept description

• LIM mode diagram

Acquisition Warm-

up

Off

Idle

FDIR/TC FDIR/TC

FDIR

TC

TC/auto TC/auto

TC/auto

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Concept description

• Mode simplification:– Off (CSL/ROB survival mode -> idem SWAP)– Idle (CSL/ROB night mode -> idem SWAP)– Warm-up (CSL/ROB stand-by mode -> idem SWAP)– Acquisition (CSL/ROB nominal modes)

• Modes not implemented in SWIM:– First swtich on: will be performed by uploaded procedure– Bake-out mode: uploaded or onboard procedure – Calibration mode: uploaded or onboard procedure, using

manually the imaging mode with different pointing configurations

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• Sequence diagram Nominal observation

Concept description

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Concept description

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Concept description

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Concept description

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•Open questions

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• Interace issues