SPACEDOS01B - Flight Model
Applications
- Space Dosimetry and spectrometry for unmanned missions
- TLR9 space dosimetry instrument - flight heritage: Sokrat-R (NORAD ID 44404) satellite
- Real-time determination of the absorbed dose in silicon and dose equivalent
- To study the material shielding
- Space Radiation Research
- Determine the LET energy spectrum of the cosmic particles
- Measure the time evolution of the radiation flux
- Operated on board of CubeSat
Main technical parameters
- Deposited Energy range: from 100 keV to 9 MeV, optionally extended to range from 200 keV to 12 MeV (divided into eight logarithmic channels)
- Measurement environment: vacuum < 3.2×10^-2 Pa
- Energy Resolution: < 50 keV/channel
- Particle types: electrons, protons, heavy ions
- Integration Time: 15 s
- Power supply: 3.3 V / 3 mA (Typical consumption: 2.6 mA @ 3.3 V)
- Interface: UART (RS232) TTL
- Temperature Stability: from -50 ℃ to +50 ℃ within error of +50 keV
- Used Sensor: HAMAMATSU S11773-02 (PIN diode 5 x 5 x 0.5 mm)
- The default configuration has a detection volume of 12.5 mm³
- H x W x L: 15mm x 41mm x 94 mm
- Weight: 33 g
Meaning of Measured Data
SPACEDOS01 measures ionizing radiation using silicon semiconductor sensor and provides energy-resolved spectral data of deposited energy. These spectral measurements form the primary measurement output of the instrument.
From the spectral data, derived quantities such as dose rate and total dose are calculated by integrating the deposited energy over the detector mass and over time. The dose rate represents the instantaneous radiation intensity derived from the measured energy spectrum, while the Total Ionizing Dose (TID) corresponds to the time-integrated dose accumulated during operation.
Spectral information enables separation of radiation components by deposited energy and supports analysis of temporal and spatial variations of the radiation environment.
All derived quantities depend on integration geometry, calibration, shielding conditions, and mission-specific configuration.
Physical dimensions
Electrical interface
The connector is a 2.54mm pitch pin header.
| Signal | Description |
|---|---|
| PD2 | Universal Input pin |
| PD3 | Universal Output pin |
| RX0 | RS232 Receive (3.3 V) |
| TX0 | RS232 Transmit (3.3 V) |
| RST# | Reset (through capacitor) |
| GND | Ground |
| 3V3 | Power supply +3.3 V |
Electromagnetic Compatibility according to ECSS-E-ST-20-07C Rev.2
Communication protocol
Sample of output data
$POSD,2a1c18d43c3937e40a3beb6c2855589b2d1a19e9
$ICSD
$DPSD,98,7fbd,36,1,0,0,0,0,0,0,100
$HKSD,9,98,800b,fe,0,0,7fbd,36,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
$BESD,4,e7,2,1,0,0,0,0,0
$ADSD,d3,3,0,0,0,0
SPACEDOS sends $DPSD, $HKSD, and $BESD messages each cca 15 seconds. The $ADSD message is sent once per day.
Communication speed is 2400 baud.
Power On
It transmits just after the power is on.
#POSD, <git hash>
This information says hello after turning the power on.
Initiation complete
Transmitted once after initialization, after powering on.
#ICSD
Initiation of the SPACEDOS HW is done. Initiation is completed up to one second after the power is on.
DPSD - SpaceDos Data Payload message
Transmitted every 15 seconds.
$DPSD, <uptime>, <noise channel>, <0.1 MeV>, <0.14 MeV>, <0.21 MeV>, <0.33 MeV>, <0.66 MeV>, <1.68 MeV>, <4.72 MeV>, <'>=9 MeV'>, <DC offset>
| Value | Length | Type | Note |
|---|---|---|---|
| $DPSD | 5 B | Char | Header |
| uptime | 4 B | Hex | Time from power on |
| noise channel | 2 B | Hex | This channel contains noise |
| 0.1 MeV | 2 B | Hex | Number of particles with absorbed energy above 0.1 MeV |
| … | … | … | |
| ’>=9’ MeV | 2 B | Hex | Overrange particles |
| DC offset | 2 B | Hex | Offset of ADC |
These messages should be stored for a long time and transmitted to the ground as a batch.
Minimal data payload (without time mark) is 18 B per 15 s => 103680 B per day
HKSD - SpaceDos HouseKeeping message
Transmitted every 15 seconds.
$HKSD, <measurement No.> , <uptime>, <filter suppressions>, <position of the 1-st channel>, <1-st ch.>, <2-nd ch.>, <3-rd ch.>,...
This is a packet with housekeeping information. Transmission of this packet is done besides other experiments’ housekeeping data. The total length of this packet should be shortened.
| Value | Range | type | Note |
|---|---|---|---|
| $HKSD | fix | Char | Header |
| measurement No. | 0..65535 | Hex | |
| uptime | 0..4294967295 | Hex | |
| filter suppressions | 0..65535 | Hex | Number of usage of digital filter for double peak suppression |
| position of the 1-st channel | 0..511 | Hex | |
| 1-st ch. | 0..65535 | Hex | Number of events in 1-st ch. |
| 2-nd ch. | 0..65535 | Hex | Number of events in 2-nd ch. |
| … | … | ||
| 50-th ch. | 0..65535 | Hex | Number of events in 50-th ch. |
BESD - SpaceDos BEacon message
Transmitted every 15 seconds. Values are zeroed after sending an ADSD message.
$BESD,<counter>, <0.1 MeV>, <0.14 MeV>, <0.21 MeV>, <0.33 MeV>, <0.66 MeV>, <1.68 MeV>, <4.72 MeV>, <'>=9 MeV'>
This message contains cumulative data for beacon transmission.
| Value | Length | Type | Note |
|---|---|---|---|
| $BESD | 5 B | Char | Header |
| counter | 2 B | Hex | Number of the beacon message |
| 0.1 MeV | 2 B | Hex | Number of particles with absorbed energy above 0.1 MeV |
| 0.14 MeV | 2 B | Hex | Number of particles with absorbed energy above 0.14 MeV |
| … | … | … | |
| ’>=9’ MeV | 2 B | Hex | Overrange particles |
ADSD - SpaceDos Almanac Data message
Transmitted after 5760 beacon messages. (approximately once a day)
$ADSD, <0.1 MeV 1 day old>, <0.14 MeV one day old>, <0.66 MeV one day old>, <0.1 MeV two days old>, <0.14 MeV two days old>, <0.66 MeV two days old>
This message contains two days of old data for beacon transmission purposes.
| Value | Length | Type | Note |
|---|---|---|---|
| $ADSD | 5 B | Char | Header |
| 0.1 MeV one day old | 4 B | Hex | Number of particles with absorbed energy above 0.1 MeV one day before |
| 0.14 MeV one day old | 4 B | Hex | Number of particles with absorbed energy above 0.14 MeV one day before |
| 0.66 MeV one day old | 4 B | Hex | Number of particles with absorbed energy above 0.66 MeV one day before |
| 0.1 MeV two days old | 4 B | Hex | Number of particles with absorbed energy above 0.1 MeV two days before |
| 0.14 MeV two days old | 4 B | Hex | Number of particles with absorbed energy above 0.14 MeV two days before |
| 0.66 MeV two days old | 4 B | Hex | Number of particles with absorbed energy above 0.66 MeV two days before |