Sensing and Control Systems of the TeamIndus Spacecraft that will land on the Moon
A look at the components that help the spacecraft compute
TeamIndus’ first spacecraft will soft-land on the Moon in 2019, one of the first attempts by any private entity. Having published an overview of the spacecraft components before, let us take a look at the sensors and control systems onboard the lander.
#1: Integrated Avionics Unit (IAU)
All the major subsystems (thermal, propulsion, power, etc.) need to be working together in a precise fashion for a successful mission. Enter the avionics unit.
The Integrated Avionics Unit (IAU) houses the modules required for electrical power systems and command+data handling. The IAU has 6 core modules:
- The Power Management System conditions and distributes electrical power to different subsystems of the spacecraft.
- The Telemetry and Telecommand (TMTC) module interfaces the spacecraft’s communication hardware to communicate with the ground station on Earth. TMTC encodes the data before sending it back to Earth. Commands sent from Earth to the lander are also decoded by the TMTC and sent to relevant modules of the spacecraft.
- The most important job of the On-Board Computing module (OBC) is to orchestrate the command+telemetry, data processing and related operations. It also processes the guidance, navigation and control (GNC) algorithms for the entire mission.
- The Thermal Control module controls all heaters depending on the data from the hundreds of thermal sensors in the spacecraft to maintain its temperature.
- The Pyro Control module supplies power to the holding mechanism to detach our rover ECA. The holding mechanism is a non-explosive actuator which holds the rover till landing. The same applies to ECA’s Japanese rover friend Sorato too.
- The Propulsion Control module enables the actuators, fires the main engine and thrusters. Cool job.
#2: Attitude determination
A host of sensors help determine the spacecraft’s attitude (orientation) in space and aid navigation.
The Inertial Measurement Unit (IMU) plays a central role in navigating the spacecraft. It consists of high precision accelerometers and gyros for detecting even the minutest amount of changes in the its velocity and/or attitude. The sun and star sensors help knowing the spacecraft’s absolute attitude in space.
These sensors aid in orienting the solar panels towards the Sun for power generation and maintain the desired attitude for main engine burns.
#3: Sensors for lunar descent
Soft landing on the Moon is arguably one of the most intriguing part of the mission. In addition to the above mentioned sensors that aid navigation, the following sensors are used during the lunar descent.
The Laser Altimeters (LALT) provide data to derive altitude during the descent phase. The Laser Rangefinders (LRF) on the other hand are used only during terminal descent i.e. when 100 meters above the lunar surface. This is the point at which the Descent Cameras (LDS) also kick in to take images of the surface.
Surface images are clicked in intervals and compared through image processing algorithms to determine velocity with respect to the ground. We have talked more about the lunar descent strategy here.
Here’s an overview of all the hardware components that compute.
With that we conclude the sensing and control systems onboard the TeamIndus lander with the IAU playing a central role.
“We had to build the lander flight software from scratch. The challenges involved were significant but we have been able to successfully design a custom made OBC that interfaces beautifully with rest of the system.” — Mardava Gubbi, Flight Software team.
We will delve into more parts of the spacecraft next. Stay tuned!