Feasibility Analysis of Payloads
Once the payload ideas are generated, the next step is identifying the best one out of them. Before approaching professors, or having all-team level meets, the person or sub-team proposing the idea should perform a preliminary feasibility analysis to ascertain that the payload doesn't have any obvious flaw or drawback. In general, the following basic checks can be performed to ascertain whether the payload is feasible or not:
- Adherence to the mission statement: As mentioned in Planning the mission and finalizing the Payload, once the mission statement is finalized, the team should stick to it. So a payload, however heavy it is, which won't adhere to the mission statement should be immediately rejected. For instance, if your mission statement is to make the world's cheapest nanosat, you won't have a heavy X-ray detector on-board.
- Complexity: . Making a satellite is a complex process in itself. Choosing a payload which will put high requirements on other subsystem would make the task even more difficult. Demonstrating cold welding in space in your first satellite would be very complex if moving parts are involved, since controlling the satellite becomes very difficult when moving parts are involved.
- Budget: One big challenge a satellite is going to face is funding. So, while deciding a payload it should be kept in mind that neither the payload instrument nor the components needed to fulfill various requirements it has imposed on different subsystems should be expensive. For example, if a payload requires high pointing accuracy which can be fulfilled only by a star-tracker, then carrying it forward is difficult as star-trackers are very expensive and purchasing them is usually beyond the scope of student satellites. Budget constraint creates one more problem. Due to their low cost, it is preferred to purchase off-the-shelf-components in place of space-grade components. Not using space-grade components results in satellite having a small life-period (between 6 months - 1 year). So, those payloads cannot be pursued which require a life-duration of more than this.
- Availability: It would not be possible to procure some payload equipments in some countries due to political issues. Hence, availability becomes an important factor governing the selection of payloads.
- Mass: Student satellites typically fall in the nano-satellite class. This means that the weight should be less than 10 kgs. Hence, a heavy payload instrument cannot be used. If you are aiming for a heavier satellite, it is advised that you obtain permissions from ISRO, or the space agency launching your satellite.
- Size: This is another important factor. For example, a synthetic aperture radar is infeasible for a cubesat due to its large antenna. There are also some size constraints that can come from launch vehicle. It is recommended that you have a rough size in mind, after due consultation with ISRO, or the agency launching your satellite. The length of each side of a student satellite is generally less than 1 ft.
- Power: Owing to their small sizes, the power generated by a student satellite is generally of the order of 1 Watt to 10 Watts. Hence, a payload which demands higher power won't be feasible.
- Orbit: Student satellites are generally launched in Low Earth Orbits. The orbits are generally polar sun synchronous. Hence, a payload requiring a different orbit would be difficult to pursue ahead, since you need a confirmation from your launching agency whether they'll launch your satellite in that orbit.
- Communication Frequencies: Most of the student satellites operate in the UHF or VHF bands. Recently, some student satellites have been launched which operate in the S band. It will be very difficult to obtain license for frequencies higher than these. This means that you cannot have exorbitantly high data rates.
' Once these basic checks are performed, some more advanced comparisons can be made using the criteria given below:
- Social Impact: Since in many cases, the money spent in making the satellite is taxpayers' money, a satellite which gives back to the society is generally preferred. If not a direct benefit to the society, at least benefit to the scientific community should be aimed for.
- Originality: If a satellite with your payload already exists, then there won't be much to be gained from your satellite except in the case where your satellite covers different geographies, or if new data is required, or if your satellite is an advancement over the existing satellite. If nothing is being gained from your satellite except your learning, pursuing that payload might not be a good idea.
- Time: 2 years is an ideal target for completing a student satellite from the day of inception. Longer the time a satellite takes to complete, more difficult it will be to ensure continuity, since the old teams will graduate and the next generation will take time to reach the level of the old team.
Once you are done reading this page, you can move on to Presenting the ideas and getting feedback
