Satellite Operations

Everything an operator does is expressed in these terms, so they come first. The classical elements are not arbitrary parameters: each one has a physical meaning — how big the orbit is, how elliptical, how tilted, where the tilt happens, where the low point sits, and where the spacecraft is along the path right now. Learn them as a picture rather than as symbols, because the entire rest of the path is spoken in this vocabulary.

Why a mission is where it is. Low orbits give resolution, short link range and low latency at the cost of speed across the sky and short contacts; geostationary buys a fixed look angle and pays in distance and latency; sun-synchronous buys consistent lighting for imaging; highly elliptical buys long dwell over high latitudes. Operationally these are completely different jobs, and the differences all trace back to the elements from A1.

An orbit is not a fixed ellipse, and this is the unit that explains most of what an operations team actually spends its time on. The Earth's oblateness precesses the orbit — which is also the effect deliberately exploited to make a sun-synchronous orbit work — while atmospheric drag decays low orbits, solar pressure pushes on large structures, and the Moon and Sun tug on high ones. Station-keeping, propellant budget and orbital lifetime all fall out of this.

🔴 The unit most amateurs get wrong. The widely available element sets are not a state vector you can integrate however you like — they are fitted to one specific analytical model and are only meaningful when propagated with it, and they carry an accuracy that degrades measurably within days. Understanding that a prediction has a shelf life, and what drives its error, is the difference between an operator and someone reading numbers off a website.

Turning orbital knowledge into a schedule. Ground tracks, rise and set times, maximum elevation, contact duration, and the difference between a barely-above-the-horizon pass and a usable one. A Skill element: the assessment is a correct predicted schedule for a real spacecraft from a real site, checked against what actually happens, which is the honest test of everything in the previous four units.

The operator's model of the vehicle. Power generation and storage, attitude determination and control, command and telemetry, thermal control, propulsion, onboard computing, and the payload the whole thing exists to serve. Learned as an interacting set rather than a list, because the operationally important facts are the couplings: attitude drives power, power drives thermal, and thermal constrains payload duty cycle.

Where the spacecraft is pointing, how it knows, and how it changes. Sun sensors, star trackers, magnetometers and gyroscopes for determination; reaction wheels, magnetic torquers and thrusters for control. The operationally critical concept is momentum management — reaction wheels absorb momentum until they saturate, and the desaturation manoeuvre is a routine, planned, occasionally troublesome operations event.

🔴 The most quantitative skill in the path and the one that most directly separates competence from vocabulary. Transmit power and antenna gain, the enormous free-space path loss, receiving system sensitivity, atmospheric and rain effects, and the resulting margin. It decides achievable data rate, minimum usable elevation and antenna size — and 'the pass failed' is very often a margin that was never there. A Skill: it is closed by computing budgets for real links, not by recalling the equation.

The physical realities of the link. Frequency bands and what each is used for and why, polarisation and the loss from getting it wrong, Doppler shift across a low-orbit pass and the tracking it demands, modulation and coding choices, and the coordination and licensing regime that governs who may transmit what and where. This is the unit that makes the previous one concrete.

The half of the system that stays on Earth. Antennas and their pointing and tracking, feeds and low-noise amplification, modems, scheduling, and the networked ground station model that lets a small operator get contacts without owning global infrastructure. Also the practical constraint that shapes every mission plan: contact opportunities are scarce, scheduled and shared.

How the operator actually talks to the spacecraft. Frame and packet structure, the standardised formats that make cross-agency operation possible, telemetry decommutation into engineering values, and command construction. The Risk element is command authentication and safety: a spacecraft that will execute any correctly formatted command from anyone is a serious vulnerability, and command sequences that are safe individually can be destructive in combination.

What the job consists of. The contact plan, pre-pass preparation, the pass itself, post-pass data handling, trend analysis over weeks rather than seconds, limit checking and alerting, procedure discipline, and shift handover. It is a procedural, documentation-heavy discipline and teaching it as such is more honest than teaching orbital mechanics and implying the rest is obvious.

Things go wrong on orbit and you cannot go and look. Single-event upsets from radiation, brownouts, stuck actuators, thermal excursions, and the autonomous safe mode that puts the vehicle in a survivable, power-positive, commandable state and waits. Recovering from safe mode without repeating the trigger is the assessed skill, and the Risk framing matters: the hazard is the recovery action as much as the fault.

The operational responsibility that has grown from a footnote into a routine task. Screening for close approaches, interpreting a probability of collision, deciding whether to manoeuvre against a false-alarm rate and a propellant budget, and the end-of-life obligation to deorbit or move to a disposal orbit. Risk elements throughout, and the mitigation half — the actual decision procedure — is what is assessed.

The capstone Skill element, and it is achievable at genuinely low cost: predict a pass for a real spacecraft, point an antenna, track the Doppler, receive the downlink, and decode the telemetry. Everything in the path is exercised at once, and the honest outcome is either a decoded frame or a diagnosed reason there is not one.