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
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