Payload

The Payload is defined as the total complement of equipment carried by a spacecraft that interacts with the subject in performance of a particular mission. Payloads are typically unique to each mission and are the fundamental reason that the spacecraft is flown. The purpose of the rest of the spacecraft is to keep the payload working and in suitable conditions (temperature, orientation, etc).

The objective of a space mission is typically to detect, communicate or interact. The subject, as an element of the space mission, is the specific thing that the spacecraft will detect, communicate or interact with.

Spacecraft missions can serve many purposes, each one with its own set of unique requirements. Nevertheless, it is possible to classify most space missions and payloads into the following broad categories: communications, remote sensing, navigation, in situ science and other. In scientific mission, the most common type is remote sensing payloads. Any observation that a spacecraft makes without directly contacting the object in question is considered remote sensing. Fundamentally we focus on measurements in the electromagnetic spectrum to determine the nature, state, or features of some physical object or phenomenon. The electromagnetic signal can be produced by the subject or reflected and it provides information about a certain feature of such subject.

Designing a payload (or any other subsystem) consists in fixing a certain set of parameters that will define it. According to the level of detail of such design, the number of parameters will vary. These design parameters allow to estimate the main characteristics and size of the payload. These main attributes, as can be the mass, power, weight, resolution, data rate, etc, allow to compare different options. They are also forwarded to the other subsystem designers so they can take into account the presence of the payload.