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1. Name, purpose, list of the units 1.2 Scientific goals 1.3 List of the units 3.2 Environmental requirements 3.3 Functional description of the experiment 3.4 Command summary 3.5 Electrical Ground Support Equipment of the SAS-2 experiment 4.2 Optional version |
5. Telemetry measurement requirements |
1. Name, purpose, list of the units
1.1 Name -
SAS-2(An ELF-VLF advanced Signal Analyzer and Sampler)
The main goal is the investigation of the ELF-VLF electromagnetic signals propagating in the Earth’s magnetosphere. Some scientific indications exist that the parameters and existence of these signals have relations to the Earth’s seismic activity. Therefore, the SAS-2 can record arbitrary shape signals in these bands and whistler signals generated by tropospheric lighting.
The detailed analysis of the fine structure of these signals could clarify the relations between the magnetosphere ELF-VLF activity and e.g. the seismic activity. Beside these the measurements planned by the SAS-2 the equipment can investigate the antropogenic modifications of ionosphere-magnetosphere region from the point of view of ELF-VLF activity, and the structure of the magnetosphere by analyzing the fine structure of whistlers.
The background of this experiment is the successful and efficient SAS-equipment, which was on board of the Intercosmos-24 (ACTIVE) satellite. The SAS-2 is an advanced version of this earlier SAS SI.
The SAS-2 itself is a single unit SI.
However, it does not contain antennas and preamplifiers. Therefore the SAS-2 must be input signals in the band 20Hz…16kHz (or 20kHz) from as other SI.
In this case the SAS-2 must get the wide-band ELF-VLF input signal form the
This is important for the interunit connections.
2. Interunit connections
3. Functional diagrams and the description of operation
This report describes the actual development state of the SAS-2 experiment in the frame of the WARNING project.
a) EXO-EM or PWP
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VLF signal input (20Hz…20kHz band, from the preamplifiers / 3 (or 6) field components. The SAS-2 will process the analogue channels using internal channel managing and 20kHz low-pass filtering.b) Satellite Power Bus Interface
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27V non-stabilized (or stabilized voltages, see chapter 0. 4. Power consumption on page *.)c) Commands Input
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Low level control of the equipment - selection of the basic modes of operation (1-3 input lines)d) Software Command & Telemetry Interface
e) Onboard Time: The time is needed to program scheduled data collections!
(To the final scientific analysis of the data, the navigation and positioning data of the satellite are necessary too.)
3.2 Environmental requirements
The SAS-2 meets the environmental requirements of the micro-satellite.
NO DANGEROUS CIRCUITS ARE IN THE SAS-2.
Mechanical parameters:
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Mass: 4,5 kg-
Size: 165 x 206 x 204 mm3.3 Functional description of the experiment
The VLF signals and the control and status information coming from the SVIST (or other SI) appear at the input of the Analogue Interface Unit. The input stage of each line is a buffer, which allows us to minimize the mutual interference between the input lines and internal circuits. The Input Buffers for the analogue inputs including analogue switch can change their input source from SVIST (or other SI) to the internal Self-test Unit. The Self-test Unit supplies a test signal for system checking.
The next stage is a Low Pass Filter because the bandwidth of the input signal may be higher than required. The cutoff frequency is 20kHz according to the sampling speed.
The advanced SAS-2 has the following basic operation modes
MODE 1: During the data collection, the equipment stores the signals of desired channels without any preprocessing. The start of the data collection in this mode is defined in onboard time.
MODE 2: In this mode the SAS-2 investigates that the input signals appearing in the three (six) input channels are a whistler or not. If the signal is a whistler, the data will be stored in the buffer-memory.
MODE DEFAULT: In this mode, the SAS-2 (or the principal investigator) selects reduced numbers or one input channel(s). The processing of this “reduced-channel” input signal could be the MODE 1 or MODE 2 versions. This mode is the default operation mode of the SAS-2 instrument.
The digital data processing unit has the following tasks:
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Software control of the data collection-
Mass memory data handling-
Setting hardware and software parameters of the experimentThe analogue signal coming from the Analogue Interface enters the 13-bit resolution sampling A/D converter. The converted data is written to the Mass Memory under the control of the Programmable Data Collection and Memory Controller. The controller is handling the timing and the data addressing procedure for the A/D and the Mass Memory. The hard core of the onboard processor is a NSC-800 (or equivalent) CPU, the input selection and fast memory-access is performed by dedicated hardware.
System Memory Organization: The system program is written in the ROM of the processor. Internal RAM of the processor is used for program variables. Some variables are stored in flip-flops of the dedicated hardware.
Mass Memory Organization: The digitized data of input channels is stored in the Mass Memory. A/D converters write Mass Memory, the samples of SAS-2’s input signals compose a continuos block in the memory. Address of input channel is added to each sample. In accordance with high data speed the input and output operation is made in large blocks at separated time segments.
Output to the Spacecraft Telemetry System: This circuitry is not implemented at present, so the SAS-2 is open for connecting with any actual communication system.
The general sketch of the data collection and transfer is the following:
The presented figure is the complete operational time-diagram of the MODE 1. In MODE 2, the operation is the same in general, however the beginning of every single data-collecting block is controlled by the automatic whistler-identifying circuit. The time-schedule of the DEFAULT MODE depends on the emergency situation.
a) Command for controlling the data collection.
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Data collection with random gap between collection-
A (Start), (N)Start - beginning of activity
N - Number of the collected block (automatic or fixed)
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Data collection with fixed gap between collection-
B (Start), (N), (Tg)Start - beginning of activity
Tg -Time gap between two collection
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Whistler detected collection-
C (Start)b) Command for channel selection:
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Channel selection: This command sets the enable bits of each analog channel-
Ch (Chen) (Ten)Chen - the enabled analog channels
Ten - permanent test channel enable
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Whistler detector selection: This command sets the enable bits of each whistler detector.-
Det (Deten)Deten the enabled detectors
c) Command for test:
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Start generating one whistler:After this command only one whistler will be created by the built in whistler generator
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Start3.5 Electrical Ground Support Equipment of the SAS-2 experiment
The EGSE is a real-time data simulator and data acquisition system. It is comprised of a general purpose and several dedicated application specific interface module. The system is able to establish all of the spacecraft hardware and data interfaces required by the experiment during the stand-alone testing and the integration of the satellite.
In the case the WARNING passive micro-satellite the SAS-2 has two power connection possibilities. We can carry out both version, and therefore we ask the chief-engineer to decide that the 0 or the 0 versions are the better for the micro-satellite.
Operating voltage: +27V, (Non-stabilized, 24V…34V)
Operating power consumption: 5W primer
SAS-2 can use the stabilized +/- 5V; +/- 12V from the central power supply unit of the satellite, instead of using the +27V power line of the satellite.
5. Telemetry measurement requirements
The SAS-2 uses an inner buffer memory of size 4Mbyte (=32Mbit). The measured data is collected into the inner buffer memory. When this memory is full, the collected data must be transmitted to the central TM of the (passive) micro-satellite. When the data transfer is finished the scientific data collection can be continued.
The analogue to digital (A/D) sampling rate is 40 kHz / channel. (In the case of ECHO-EM: 3 channels exist, in the case of PWP: 6 channels exist.)
The speed of the data transfer between SAS-2 and the satellite TM system is planned to be 20Kbit/sec. (The parameter can be modified not later than the first quarter of 1998.)
The required long range (>24 hours) data rate on satellite to Earth central TM channel:
The data mass: 20…40 MBit/orbit
The used mass of commands: cca. 48 bit/orbit
The SAS-2 can and will operate on every part of the orbit. Theoretically, the continuous operation would be the best, but the SC TM capacity limits the real data collection time. Therefore the SAS-2 has the following operational modes:
Operation MODE 1 and 2: Data collection starting at a given on-board time (see chapter 0. 3.3 Functional description of the experiment on page *).
Default operation: Data collection from reduced number of input channels starting at a given on-board time.
(For more details see chapter 0. 3.3 Functional description of the experiment on page *).
The general description of the control requirements is given in the points 0. and 0.
There are the followings:
8. Volume and sequence of works at mounting
SAS-2 does not need any adjustment before mounting to spacecraft.
From the beginning of the satellite integration:
The SAS-2 equipment does not contain antennas (see chapter 0. 2. Interunit connections on page *).
Optionally: In a special test mode, the SAS-2 can generate external and / or internal whistler signal. For the external test signal, a small ferrite antenna must be installed on outside of the box.
SAS-2 will be mounted to the spacecraft by 4 screws (see chapter 0. 10. Outline drawing on page *). Size and position of the bore may be modified in a small compass.
Electric sockets of SAS-2 will be connected to the source of input channels, to power system, telemetry channel and control channel of spacecraft (see chapter 0. 2. Interunit connections on page *). The position of these sockets is given in chapter 0. 10. Outline drawing on page *.
Important: The heat originated in circuits of SAS-2 will be led off across the baseboard of SAS-2 equipment. This surface is the heat-connection to the SC and gives the opportunity of heat-stabilization of SAS-2.
12. Technical-and-economic index
We can not understand precisely the real meaning of this point and we have not any answer to our question about this point from the YUZHNOYE. Therefore in this moment we can not give a detailed text in this point.
13. Reliability characteristics
The SAS-2 SI is built purely from electronic components, and does not contain any moving part or decrescendo material. In the SAS-2, no “dangerous circuits” are present.
The planned lifetime is about 5 years.
14. Evaluation of the technical level and novelty
The scientific goals of the SAS-2 experiment and the scientific possibilities guaranteed by the SAS-2 equipment are at the front line of the actual research. The possible relation between ELF-VLF magnetospheric phenomena and the seismic activity of the Earth is not clear today, and this is a very important open question in science.
The technological level of the SAS-2 equipment is an advanced one. The conceptual and electrical construction of SAS-2 equipment is a middle-level version of high-tech solutions.
15.
The KFKI Research Institute for Particle and Nuclear Physics (RIPNP) is ready to examine the possibility of preparing the onboard data acquisition and control computer for the passive subsatellite of the WARNING project. The real design and development can be started after the exact definition of the tasks and requirements. The estimated development time is two years.
A possible data acquisition and control computer (DACC) for the passive subsatellite will have the following preliminary main parameters.
1. The architecture of the DACC will have a redundant cold structure, as it is a part of the service system and have to have high reliability. The DACC consists of the following functional subunits: Processor Unit (PU), Mass Memory (MM), Radio Interface (RIF), and Instrument Interface (IIF). Each subunit will have the same redundant units and they will work in cold redundant mode.
2. Each Processor Unit consist of
- Microprocessor (16 bit),
- Fuse PROM, 4 k word (1 w = 16 bits),
- EEPROM for program (32 kword),
- RAM for temporary data (32 kword).
All memory types contain an Error Detection and Correction Circuit, so they are protected for the random failure with Hamming Code.
3. The Mass Memory is the temporary science data storage unit, which has no Error Correction Circuit. The baseline capacity is 16 MBit TBC. It has latch-up protection.
4. The Radio Interface will have a hardware decoder to handle a limited number (8) direct uplink commands. The expected downlink telemetry speed is 1 MBit/sec.
5. The DACC will have Central Interface Unit (CIU) for the communication with the Instruments. Each Instrument will have Remote Interface Unit (RIU) for the communication through the serial Interface.
6. The estimated mass is 2.5 kg and the estimated power consumption is 3 W of the DACC.
7. The DACC fulfills the following tasks:
- Telecommand (TC) decoding, verification and distribution,
- Storage and execution of time tagged TC sequences,
- Distribute the onboard time,
- Acquisition of science and housekeeping data from the instruments,
- Temporary storage of the instruments data stream in MM,
- Format Telemetry (TM) frames, including header and error protection words,
- General purpose data compression,
- Transmit TM frames.
8. The core of the onboard software will be a dedicated real-time multitasking system. It will have two operation modes: ground test mode with debugging possibilities and the real onboard mode.
The previous parameters are predicted on the base of the earlier mission's experience, where the KFKI RIPNP participated in the realization of the central data acquisition and control computer development. In the Phobos mission was developed the redundant central computer for the Lander: it weighted 2 kg, power consumption was 1 W, the mass memory had 96 Kbytes, the TM speed was 32 bit/sec, and microprocessor was 8-bit type. The central computer of the Spectr-X-Gamma mission has a double redundancy and it has a separate MM, it has 16-bit type microprocessor, redundant data acquisition bus, and galvanicaly isolated subunit architecture.