Space Missions—I

We previously defined space-based technology as “…any technical capability that incorporates a man-made extra-terrestrial segment in its intended operation here on earth…” Consequently, the discussions here will dwell on the “man-made extra-terrestrial segment.” In simple terms, this rather mouthful of an expression refers to an artificial satellite purposely built and launched into a predefined orbit to perform a specific specialized function(s).

The projectable collective campaign involving formulation and implementation of an artificial satellite in orbit is what we refer to as a Space Mission. Space missions are normally bound by a finite amount of time and typically terminate when the spacecraft is rendered incapable of performing the original intended objective. A gradual or sudden degradation of spacecraft systems leading to mission termination can occur at the expected or unexpected juncture in the planned mission timeline. For instance, a sudden explosion of the spacecraft propellant tank in orbit is a sudden system degradation; while continued decrease in sensing ability by a particular sensor is a gradual degradation example.

Space mission segments

Space missions are customarily initiated in many different ways. Though there is no single avenue to initiate a space mission, all missions are instituted to address an established collective need(s). For instance, purely scientific missions tend to originate from the scientific community; communication missions may be initiated by the government to fulfill a national communication need or a commercial company to generate revenue; a small educational satellite mission may originate from higher institution of learning as a pedagogical tool and so on.

The life-cycle of a space mission normally evolves through four broad phases. A slight variation in the nomenclature of these four phases is evident among different countries and cultures. However, in spite of these deviations, adherence of the respective space mission life-cycle to these four broad phases is maintained.  The four phases of a space mission life-cycle are:

  • Concept exploration—feasibility and concept development phase which comprises preliminary systems design and mission analysis. A wide characterization of the space mission is realized at this stage.
  • Detailed development—formal detailed definition and design of the various system components is achieved.
  • Production and deployment—all the system components comprising the ground, launch and space segments are fabricated then deployed in their respective roles to realize a sound mission performance.
  • Operations, support and disposal—normal day-to-day operations of  maintenance and support of the mission. The space segment is decommissioned to indicate end of mission in this phase.

Transition from one phase to the next in the mission life-cycle is regulated through Key Decision Points in the form of formal reviews. These reviews determine whether the process should proceed form one phase to the next or if modifications are necessary.

Relatively simpler space missions can take 12 to 18 months to develop then are operated for a period of 6 months to several years. Large complex space missions however typically take 10 to 15 years to develop and maybe operated for 5 to 15 years.

The second installment of this post on Space Mission will explore space mission classification and space technology capability hierarchy.

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