• Mayur Pawar

Do you know: How space missions get planned and coded?

Updated: Jul 29, 2020

Ever since I was a kid, I was always curious to know about space missions, how space missions get planned? How they develop spacecraft according to the mission? Many things about it. But, as I gradually grow up, I get the answers to many of these questions and had the opportunity to work on some of the real missions and still are. So, let's get started with the topic.

Firstly, the mission planning. The very first step of any space mission to determine mission objectives and mission statement, which govern by the board of space agency. According to it, mission requirements get in sound. There can be a number of mission requirements. Functional requirements refer to the performance of the system to perform the mission, which includes factors affecting preliminary mission, payload size, orbit, state vector, the complexity of the mission, number of payloads (Orbiter, Lander, Rover, Probe, etc), scheduling, communication architecture, processing delays and launch vehicle capability. Secondly operational requirements, it is typically mission operational requirements, which include duration, level of redundancy, survivability in terms of orbit, electronics, etc, also refers to data distribution and form of data transmitted through the system.

Next step in mission planning is the concept of operational tacking, building & developing systems. Data delivery is the most comprehensive part, it includes data generation or collection while in service, processing and converting it into the deliverable formats and transmit it to the ground station. In data delivery there are key trade-offs includes Space vs. Ground processing; Level of autonomy; Central vs. distributed processing. In Space vs. Ground, 'how much of the data processing occurs onboard the S/C vs. how much is done at mission operations or by the end-user?' the thinking required and in Central vs. distributed processing, 'is one computer talking to another computer, or does one large central computer on the S/C or on the ground process everything?' required. Tracking includes tasking, scheduling and control, how the system decides what to do in the long term and the short term (e.g., Which sensors are active and when is data being transmitted and processed?). There are common system drivers like design and manufacturing cost, power generation, onboard data storage and processing, overall system accuracy, operational cost; communications; size of the team. After clarifying the requirements and concept of mission, proposals determine the cost of the mission and schedule the mission.

Choosing the most appropriate mission subject is an important part of the overall mission design. For example, the trade-off process

  • Determine fundamental mission objective(s) (e.g. probe having objective to find water on Mars)

  • Determine what possible subjects could be used to meet these objectives. (Telescopic observed surfaces, polar regions, etc)

  • Determine broad ways the S/C can detect or interact with possible subjects ( Heat => IR; renging frequncy detection => visual, composition => light detection and ranging (lidar) )

  • Determine whether multiple subjects and payloads should be used (Not initially)

  • Define and document initial subject selection (IR detection of heat or chemical composition)

To get to know more about how satellite system integrated within and works together for the mission accomplishment you much read article on the satellite systems from here.

Now let's get to another half of our article. The coding! In-ground station telemetry programmed as per the mission requirements. There are certain levels and types of programming required to satisfy payload smooth operation and to position it in a specific mission window. Various subsystems need to program from scratch whereas for precise data collection, algorithms to be added. For propulsion system, there are separate sensory panels and sensors assigned with engines, fuel tanks, thrust control module and valves. Propulsion sensory panel coding differs for every other launch vehicle and spacecraft according to the march, aerodynamic structure and other properties. Then there is altitude and state vector control which determine telemetry of the flight and relative motion of the chaser vs. the target. Strategy to successfully achieve a rendezvous in orbit. Navigation and guidance is the core of the satellite operation, there is the navigation uplink & downlink connected to GNC module (Autopilot of spacecraft) of the satellite to navigate itself while launching, in orbit or manuvering. Controllers there to get back on track if the satellite gets deviated. It is a part of error correction and increasing mission reliability.

There are various programming languages and operating system used by engineers for different kind of operations and system development. Linux is the most favourite operating system for engineering system, whereas windows also used in a wide range of applications. Programming language depends upon processing unit and system requirement. JAVA, C, C++, & Python are kinda used in various operational systems, besides these commonly and widely used programming languages there are certain programming languages which are typically dedicated to performing engineering work and space application development like MATLAB, Ada, LabVIEW, VHDL, FORTRAN, NASA's HAL/S, etc.

Programming of the mission is typically done by the timeline of the mission, as the mission progresses ground station uploads further instructions to onboard computers. The vehicle code is on the order of a couple of hundred thousand lines. Vehicle code refers to the whole integration of the main four parts to the launch vehicle or spacecraft Structural system, payload system (Incase of spacecraft instruments onboard), guidance system and propulsion system. All codes firstly analyse, tightly reviewed and simulate multiple times to generate accurate outputs.

Space missions seem to be very enthusiastic and interesting but there are many critical systems subsystem are involved to ensure the safety of spacecraft ultimately of the mission.

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