STEP 1 · structure
Spacecraft Bus (LEOStar-3)
The bus is the satellite's body — the frame that everything else bolts onto.
Why it exists: Every camera, battery, and antenna needs something solid to sit on and wires to connect through, and the bus is that skeleton.
Without it: With no body to build on, there is nowhere to mount a single instrument or part.
For engineers: Structural flexure maps directly into geolocation error, so the deck is designed for alignment stability across each orbit's thermal cycle; reflying Landsat 8's qualified platform cut development risk for a 5-year design life with consumables sized for well over a decade.
The same LEOStar-3 bus design flew on Landsat 8 in 2013, so Landsat 9 is essentially a proven satellite built a second time — a deliberate choice to keep the decades-long Landsat record unbroken.
Source: Northrop Grumman — Landsat 9STEP 2 · power
Battery & Power Electronics
The battery stores electricity so the satellite keeps working even when it flies into the dark side of Earth.
Why it exists: For part of every orbit the satellite is in Earth's shadow with no sunlight, so it has to run on saved-up power.
Without it: Without a battery, everything shuts off the instant the satellite passes into darkness.
For engineers: Nickel-hydrogen chemistry tolerates LEO's relentless duty — roughly 5,000 charge-discharge cycles a year — while the power electronics hold the regulated bus steady through eclipse entry and exit transients and peak loads like the TIRS-2 cryocooler.
Landsat 9 slips through Earth's shadow during part of every 99-minute orbit, so its battery is charged and drained on the order of a dozen times a day, every day, for years.
Source: NASA Science — Landsat 9 Mission DetailsSTEP 3 · propulsion
Hydrazine Propulsion System
Small thrusters give the satellite tiny nudges to stay exactly on its planned path.
Why it exists: A satellite that photographs the same places over and over has to hold its track precisely, and thrusters make the little corrections.
Without it: Without thrusters the satellite slowly drifts off the exact path it is supposed to follow.
For engineers: Precise, repeatable pixel geometry over decades depends on holding the ground track tightly against drag and perturbations.
Landsat 9 and Landsat 8 fly the same orbit eight days apart, so the ground track has to be held precisely — keeping the two satellites in that shared rhythm is part of the propulsion system's job.
Source: NASA Science — Landsat 9 Mission DetailsSTEP 4 · attitude
Attitude Determination & Control
This system keeps the satellite pointed the right way — cameras at the ground, solar wing at the Sun.
Why it exists: A camera that is wobbling or facing the wrong direction takes useless, smeared pictures.
Without it: Without steady pointing the satellite tumbles, the pictures blur, and the solar wing loses the Sun.
For engineers: Sub-pixel geolocation from 705 km demands attitude knowledge and stability far finer than the ground sample distance.
To keep a pixel on the ground where it belongs from 705 km up, the satellite has to know which way it is pointing to a tiny fraction of a degree — its star trackers photograph the star field to work that out.
Source: NASA Science — Landsat 9 Mission DetailsSTEP 5 · thermal
Thermal Control & Cryocooler
Radiators and a special cooler get rid of heat and keep the heat-camera icy cold.
Why it exists: Electronics make heat, and the thermal camera can only see heat if it is kept much colder than what it is looking at.
Without it: Without cooling the satellite overheats and the heat-camera is blinded by its own warmth.
For engineers: QWIP detectors only sense thermal-infrared signal when cooled to 43 K; a warm detector is swamped by its own thermal emission.
One radiator dumps the cryocooler's heat while a second holds the TIRS-2 telescope at a steady 185 K (about -88°C) — a camera that has to be kept cold in order to see heat.
Source: NASA Science — Thermal Infrared Sensor (TIRS)STEP 6 · optics
Operational Land Imager 2 (OLI-2)
OLI-2 is the main camera — it takes the colour and near-infrared pictures of the land below.
Why it exists: The whole point of Landsat is to photograph forests, farms, cities, and coastlines, and OLI-2 is the eye that does it.
Without it: Without OLI-2 there are no ordinary land pictures at all — the satellite is flying blind.
For engineers: The push-broom architecture with no scan mirror gives higher signal-to-noise and radiometric fidelity than the older whisk-broom Landsat 7 design.
OLI-2 has more than 7,000 tiny detectors lined up across each band, so instead of sweeping a mirror it simply glides over the ground like a push-broom, capturing a 185-km-wide strip in one pass.
Source: NASA Science — Operational Land Imager (OLI)STEP 7 · instrument
Thermal Infrared Sensor 2 (TIRS-2)
TIRS-2 is the heat camera — it measures how warm or cool the ground is.
Why it exists: Heat maps show which fields are thirsty, where wildfires burn, and how cities trap warmth.
Without it: Without TIRS-2 the satellite still sees colour, but it can no longer feel temperature.
For engineers: Two thermal bands let processing separate surface temperature from atmospheric effects, correcting the stray-light issue seen on Landsat 8's TIRS.
TIRS-2 sees heat using quantum-well infrared photodetectors chilled to 43 K — about -230°C, colder than the surface of Pluto — because a warm detector would be blinded by its own glow.
Source: NASA Science — Thermal Infrared Sensor (TIRS)STEP 8 · comms
Solid-State Recorder & Data Handling
The recorder is the satellite's memory — it saves pictures until they can be sent home.
Why it exists: The satellite takes far more pictures than it can beam down at once, so it has to store them for later.
Without it: Without memory, any picture taken away from a ground station is simply lost.
For engineers: A station contact lasts only minutes, so the recorder must ingest about 750 scenes a day, record and play back simultaneously, and retain every scene until ground receipt is confirmed — that store-and-forward margin is what lets acquisition run nonstop.
Landsat 9 collects around 750 scenes a day — far more than it can send down in real time — so a solid-state recorder holds them until the satellite flies over a ground station.
Source: USGS — Landsat 9STEP 9 · comms
X-Band Downlink Antenna
The antenna beams the pictures down to receiving dishes on Earth.
Why it exists: A picture nobody can download is useless, so the satellite needs a radio to send everything home.
Without it: Without the antenna the images are trapped on board and never reach anyone.
For engineers: The fixed earth-coverage pattern trades antenna gain for reliability — no gimbal to fail, contact whenever a station is in view — with the data rate sized to drain the recorder within a pass of only a few minutes.
Landsat 9 sends its pictures to Earth over an X-band radio link, where USGS turns them into the free, public imagery that anyone in the world can download.
Source: NASA Science — Landsat 9 Mission DetailsSTEP 10 · power
Deployable Solar Array
The solar wing turns sunlight into the electricity that runs the whole satellite.
Why it exists: There are no power outlets in space, so sunlight is the only fuel the satellite has.
Without it: Without the wing there is no power source, and once the battery empties everything goes dark.
For engineers: The wing is sized to run imaging and cryocooler loads while still recharging the battery within each sunlit arc, and its sun-tracking drive introduces a slow disturbance torque the reaction wheels must absorb — the price of keeping one wing fully lit.
The single solar wing swivels to track the Sun as the satellite orbits, and every image Landsat 9 has ever taken was powered by sunlight it had collected moments earlier.
Source: Northrop Grumman — Landsat 9