The LARES A&H/SS is the payload environmental data acquisition, satellites’ separation and telemetry transmission core adopted for the first series of test launch of the VEGA booster: the first mission where is involved the LARES A&H/SS is called LARES mission.
The LARES A&H/SS comprise hardware, software and firmware to perform those major functionalities:
- VEGA controlled payload satellites separation;
- Payload environment sensor acquisition and transmission in telemetry stream;
- VEGA and Payload shocks recording with high frequency sensor and deferred telemetry transmission;
- LARES A&H/SS health and diagnostic data transmission;
- VEGA deployed sensor acquisition and transmission in telemetry stream;
- Payload video camera acquisition and transmission in telemetry stream;
- VEGA video camera acquisition and transmission in telemetry stream;
- VEGA and Payload high frame rate video cameras recording with deferred transmission;
- Energy storage and entire payload power supply distribution;
- Harness for payload and VEGA I/Fs connection;
- I/Fs for ground operations.
The LARES A&H/SS will be developed to achieve all the LARES mission goals that are:
Primary objective: release of LARES satellite in its operational orbit and conditions
Secondary objective: support the LV qualification performing the acquisition of LV-related parameter data/video in the LV Payload area and fairings and transmit to the ground via telemetry the acquired data/video.Support the LV qualification performing high sample rate shock events acquisition and recording characterizing the actual Payload environment for future missions. Support media impact of LARES mission and first VEGA qualification flight with high frame rate video cameras acquisition.
Additional mission functions: Carry and release Secondary Payloads represented by 7 CubeSat micro-satellites and the ALMASat-1 satellite.
Due to the particularity of the LARES mission primary target, the LARES A&H/SS focus redundant architecture concepts in the separation chain; the acquisition section is developed to reduce, with no redundancy to minimize the LARES A&H/SS weight, the mission degradation in the eventuality of failures of a subsystem component.
The LARES A&H/SS functionality could be summarized as follows:
– Energization of the separation devices to permit the correct deployment of the payload satellites: the subsystem receives four dry-loops from the VEGA launch vehicle that specifies some mission phases. The LARES A&H/SS uses these commands to perform satellite separation maintaining a high safety margin. A proper separation energy storage unit and related harness is also part of the A&H/SS.
– Transmission of the information that concerns the separation actuation: the LARES A&H/SS will extract some measures from the separation chain that indicates the separation status. Those measurements reflects the separation logic state (input dry-loops level, registers, safety barriers, actuations) and also the separation energy that will be injected to the separation devices in terms of current and voltage. To perform transmission, the LARES A&H/SS integrates an S-Band transmitter compliant with the RF requirements for the mission, and all the necessary logic circuitry to provide telemetry encapsulation and encoding.
– Acquisition of LARES environmental sensors and some environmental LV sensors: to support the LV qualification, the LARES A&H/SS offers a complete analogue acquisition platform that could handle various type of sensors such as:
- Acoustic Pressure;
- High sample rate shock accelerometers;
- Heat Flux;
- Strain Gages;
For some of those sensors the conditioning stage is external and the LARES A&H/SS will provide proper power supply; for others the conditioner is part of the acquisition equipment. The conditioner supply lines were continuously monitored in order to prevent anomalous events cutting the voltage feed. The acquisition segment of LARES A&H/SS is powered by its own battery source that is integrated in the subsystem.
– Transmission of the acquired sensors measures: the LARES A&H/SS performs CCSDS compliant data transmission of the sensors connected to the subsystem. The S-Band transmitter is excited with a PCM-NRZ-L CCSDS telemetry stream that is formatted accordingly to the LARES mission Data Handling Timeline.
– Video Cameras acquisition, recording and video stream transmission: the LV mission will be video recorded thanks to an external video camera mounted at the top of the booster in the external part of the AVUM module. The external video camera signal is acquired by a dedicated acquisition unit section, part of the A&H S/S: this unit is able to handle up to two video cameras. The other video input is reserved for an internal video camera that is set to frame the LARES satellite separation and deployment event (see Figure 3.2). The acquisition unit also performs video stream compression, concordantly to the wavelet JPEG2000 standard algorithm, and digital stream transmission to ground. Particular video acquisition, that are also treated with and higher reliability, could be acquired with an higher frame rate and stored inside the DSU board for further ground transmission. The video cameras are electrically powered by the LARES A&H/SS too.
– Physical measures of environmental condition: to support the LV qualification, the LARES A&H/SS includes the greater part of sensors deployed in the payload to outline the environmental specifications for the future use of VEGA as a carrier. The sensors are: accelerometers, microphones, heat-fluxes and temperature probes.
– Supply, handling and distribution of the electrical power required by the subsystem: one of the unit of the LARES A&H/SS is a high capacity Li-ION multiple battery pack that store enough energy to perform the entire mission without recharge. The LARES A&H/SS include a power distribution unit voted at electrical power management, loads and batteries detaching, power supervisor and as interface between EGSE and batteries during recharging process.
– Provide proper electrical and mechanical I/Fs with the other LARES system components: the LARES A&H/SS will be designed to fit perfectly with the mechanical I/Fs offered in the SSUP satisfying the environmental requirements of the LARES mission. To be compliant with the other parts of LARES system and, in general, of the VEGA LV, the LARES A&H/SS electrical I/Fs must be fully compatible with the electrical counterpart of the interface. Specific tests and simulation bench will be adopted during the qualification campaign of the subsystem.
– Supply ground support equipment: prior the launch of VEGA LV, the LARES A&H/SS will be transported in the test facilities for partial integration in LARES system and at the CSG space centre for the final integration on the AVUM module at the top of the booster. To solve transportation and integration steps of the mission, customized transport container and test equipment must be developed. The transport container will be constructed suiting all the requirements for safe handling and carrying without LARES A&H/SS degradation. The battery pack of the LARES A&H/SS will be electronically detached from loads to provide enough time for any transpiration step without exceeding the 30% of DOD: this kind of loads cut off will allow maintaining the battery pack harness always linked without any unplug of connectors (with except for long time transportations). For ground support operations a dedicated EGSE will be developed to perform LARES A&H/SS boards, equipment and subsystem test, qualification, maintenance and pre-launch configuration and monitoring. Test fixtures and test harness will also be worked out to enable checks and analysis in the chosen test facilities.
The partially assembled LARES system is presented in Figure 3.1: the base plate (SSUP) is formed by four petals to permit an easiest manufacturing, handling and transportation.
LARES satellite and its separation subsystem occupy most of the payload area and weight.
As explained above, the LARES A&H/SS will monitor the payload environment and control all the payload electrical parts and I/Fs.
The populated shows the entire first VEGA launch payload:
1. LARES A&H/SS equipments
2. LARES satellite with its separation system (SSEP)
3. LARES A&H/SS sensors’ conditioners
4. Almasat satellite
5. Cubesat dispenser 1
6. Cubesat dispenser 2
7. Cubesat dispenser 3
8. Payload sensors brackets
9. LARES A&H/SS P/L adapter I/Fs connectors
LARES system SSUP
LARES A&H/SS petal
The equipments that form the LARES A&H/SS are:
1. Acquisition & Processing Equipment A&P/EQ
2. Distribution & Separation Equipment D&S/EQ
3. Battery Pack Equipment BAP/EQ
4. Telemetry Equipment TLM/EQ
5. Internal Video Camera
Other components of LARES A&H/SS are:
7. External Video Camera
The LARES A&H/SS equipments functionalities are expound as follows:
– BAP/EQ: is the energy storage part of the A&H/SS. The battery pack contains three kinds of Li-ION accumulators. Two of them are perfectly equal and are assigned to the satellites separation chains. The other battery will power supply the acquisition section and the attached sensors, conditioners, video cameras and telemetry transmitter.
The BAP/EQ is provided with housekeeping I/Fs used to monitor and control the EGSE recharging process and to check the battery pack status during the LARES mission.
– D&S/EQ: is the equipment voted to satisfy completely, with the battery pack, the primary objective of the LARES mission. This equipment performs the energization of the separation devices adopting redundancy concepts and particular firmware strategies to achieve a high probability of success without waiving in the safety. The D&S/EQ uses four dry-loop inputs as commands to actuate the separations. Those commands are provided by the LV and indicates particular and significant mission phases:
I. Lift Off: instant when the VEGA launch vehicle leave the ground pad;
II. Fairing Separation: moment when the VEGA LV start the fairing opening sequence;
III. LARES Separation: instant at which must start the four LARES separation devices energization;
IV. Secondary Payload Separation: marker that will initiate the timed release sequence of the 3 Cubesat dispensers and the Almasat satellite. When the latest satellite will be deployed, starts the batteries passivation sequence.
With the commands above, the D&S/EQ will base particular strategies to maintain a high safety margin, to avoid the energy injection in instants different than the desired ones, and also a high probability of success.
The other function of the D&S/EQ is the power distribution to the other parts of the subsystem. Starting from the connection to the acquisition battery, the D&S/EQ extracts the power supply for the acquisition equipment and for the telemetry equipment: proper control signal coming from the LARES A&H/SS EGSE and from the acquisition equipment could enable or disable some of the power distribution outputs.
– A&P/EQ: is the acquisition and processing core of the A&H/SS. It performs as I/F to the analogue sensors with conditioning and digitalization of the measured signal. Each digital conversion process will be time-stamped to permit different channel alignment with absolute time reference. Two of the sensors managed by the A&P/EQ are video cameras: the analogue video signal is converted into a JPEG2000 compliant frame stream, time-stamped and prepared for transmission. Thanks to the DSU board it could be possible to store up to 8 video sequences with a frame rate of 12.5fps that are transferred in a deferred manner w.r.t the Data Handling Timeline.
4 of the 12 acceleration sensors are acquired with a high sample rate (up to 1MS/s@1s recording time) in order to handle time-limited shock events by the FAU boards. Each FAU board could record up to 4 shock events that are transferred to ground as specified in the Data Handling Timeline.
The A&P/EQ had in charge also the telemetry stream preparation: from an encoding point of view, the telemetry stream is compliant with CCSDS specification and the baseband format is PCM-NRZ-L with a gross bitrate of 1Mbit/s.
The telemetry stream payload is formatted accordingly to the Data Handling Timeline: sensors acquisition is time-controlled and based to the mission phase steps. For the time-control, the A&P/EQ re-align the pre-programmed mission phases thanks to a connection with the D&S/EQ: the signals used to rule the separation process are replicated by the D&S/EQ and transmitted to the A&P/EQ.
All the sensors or sensors conditioner, power supply is managed by the A&P/EQ including the video cameras; in this way the A&P/EQ reduce the energy consumption shutting down the sensors that aren’t required in a particular mission phase in the Data Handling Timeline. The sensors power control is also used to prevent faulty conditions: each sensor power supply I/F is continuously monitored by the A&P/EQ and, in case of strange behaviour in current absorption, the power supply output will be turned off preserving the functionality of all the others.
– TLM/EQ: is the RF transmission section of the A&H/SS. It performs RF carrier FM modulation of the baseband stream prepared by the A&P/EQ. The transmitter is calibrated at 2218MHz with an output power of 10W.
For safety reasons, the RF telemetry transmission is controlled by two independent safety barrier electronic switches installed in the D&S/EQ that will be driven by the A&P/EQ: the RF irradiation will be activated only at the reception of the Lift Off command; before this moment, only the EGSE operator could override the safety protection.
Power Signal paths are marked in Black and generally represents high current connections (power supplies and separation signals). Control Signals paths are marked in Blue and generally represents configuration and control signals. Telemetry Signal paths are marked in Red and generally represents all the signals that transport information useful to constitute the final RF telemetry stream.
LARES A&H/SS Architecture
The key player of the LARES A&H/SS is the A&P/EQ but the core for the mission primary object is represented by the D&S/EQ: A&P/EQ acts as master for all the telemetry processes and the D&S/EQ works especially in the separation procedure.
The D&S/EQ, when the umbilicals were disconnected, works as standalone and the only control inputs are acted by the VEGA LV commands group; the Control Signal Path from the A&P/EQ to the D&S/EQ, that is marked as a dashed line, is referred to the power section of the D&S/EQ to remove the two safety barriers to power up the TLM/EQ.