Star Tracker DSP code and operations (current status)

Program Memory Error Protection Parity Check: booter->loader CRC: loader->main program

Firmware Update Acquisition commands implemented and tested (cameras on/off, image

buffer selection, acquisition) Data Reduction Algorithm implemented (centroid and standard deviations

of the 10 brightest detected stars) Epoch Gate Handling Commands (ast_newEpoch, ast_endEpoch) Automatic Acquisition (we can download data while acquiring) Reduced Data Buffer (current depth 100 frames, increasable up to ~1000) Monitoring and general control commands (Clock, Housekeeping, … )

People: M. Sarchioni, G. Alberti, A. Lebedev, E. Fiandrini

Standard Work Cycle

DAQwork flow

Data Reduction Algo.

Each frame (512x512 pixel a 12 bit ≈ 384 KB) reduced to ~ 110 byte (can vary in future)

Returns: Centroids and Standard Deviations of the

10 brightest stars' cluster (7 bytes per star) Time stamp (milliseconds from last epoch) Absolute Time of the last epoch (seconds

from 01/01/1970 and milliseconds)

Data Reduction Algo.

Data Reduction Algo.

Data Reduction Algo.

Data Reduction Algo.

Data Reduction Algo.

Data Reduction Algo.

Data Reduction Algo.

Data readout(guidance by A. Lebedev)

• raw data size is huge (262144 pixels, 524288 bytes)

• limited serial port comunication (19200 baud)

• output from ASTE goes to USCM buffer memory, 4096 bytes

• compressed data ~ 110 bytes per frame

• internal ASTE buffer contain 100 compressed frames

• every time data are requested to ASTE, it deliver a fixed maximum number of frames (37) and the backlog

• with a periodic reading of the buffers (ASTE and USCM) every ~ 5 second we do not expect any data loss

Data readout status and action

• test completed on FS set-up with ‘fake’ data (no cameras)• readout scheme implemented also on the flight

software

• test compressed data readout procedure on flight hardware• finalize readout procedure for flight• define and test raw data readout procedure

Epoch Handling

Procedure to set a new epoch:

• Voiding the previous epoch setting the value to 0 with the ast_newEpoch command

• Reset Pulse occurs

• ASTE receives temporal informations of the pulse and sets the internal epoch (with the ast_newEpoch command again)

To Do Download some raw images:– in flight for algorithm tuning

– SNR – CCDs faults– Tresholds

– on ground– develop procedure and measure download time

Epoch Issue– Pulse per Epoch – Temporal information about every pulse– Find a compromise for the temporal interval

between (reset) pulse (clock drift vs. lost frames)

Some Image

Some Image