Constellations and orbits

A constellation is a set of satellites designed and operated as one system. What makes it a system rather than a collection is that the orbits are chosen together, so the gaps between them are distributed rather than concentrated.

The parameters that matter

Four numbers determine most of a constellation’s behavior. Everything else is refinement.

Parameter	Controls	Trade
Altitude	Footprint size, path loss, orbital period, drag	Higher sees more per satellite but costs link margin and delays revisit
Inclination	Which latitudes are covered at all	Higher reaches the poles but concentrates less time at mid latitudes
Number of planes	How coverage is distributed in longitude	More planes cost more launches
Satellites per plane	How coverage is distributed along track	More satellites shorten the gap within a plane

Inclination sets a hard ceiling on latitude coverage. A 53-degree constellation never passes over the poles, so no number of satellites will cover them. This is the single most common surprise in a first design, and it shows up as a coverage minimum of zero percent while the mean looks healthy.

Planes and shells

A plane is one orbital ring. Satellites in the same plane share an inclination and altitude, and differ only in where they sit around the ring.

A shell is a group of planes sharing an altitude and inclination, spread around the Earth in right ascension of the ascending node. A real system often uses several shells at different inclinations, precisely because one inclination cannot serve every latitude well.

The two angles that place a satellite:

Angle	Places the satellite	Range
RAAN, right ascension of the ascending node	Which plane, by where the orbit crosses the equator going north	0 to 360 degrees
True anomaly	Where in the ring, along track	0 to 360 degrees

Walker patterns

Walker patterns are a standard way of distributing satellites so that coverage gaps are spread evenly instead of clustering. They are described by three numbers, conventionally written $i: t/p/f$ .

Symbol	Meaning
$i$	Inclination, in degrees
$t$	Total satellites
$p$	Number of planes
$f$	Phasing factor, an integer from 0 to $p-1$

Planes are spaced evenly in RAAN, and satellites are spaced evenly in true anomaly within each plane. The phasing factor offsets each plane relative to the one before it, so satellites in adjacent planes do not all cross the equator at the same moment.

\Delta\Omega = \frac{360^\circ}{p}, \qquad \Delta\nu = \frac{360^\circ \, p}{t}, \qquad \text{offset} = \frac{360^\circ f}{t}

Delta and Star

Pattern	RAAN spread	Character
Walker Delta	Planes spread over 360 degrees	Even global coverage between the inclination limits. The usual choice for broadband and Earth observation
Walker Star	Planes spread over 180 degrees, near-polar	Planes converge over the poles. Strong polar coverage, with a seam where ascending and descending planes meet

A Star pattern at high inclination gives excellent polar coverage and a counter-rotating seam where relative velocities between adjacent planes are large, which matters for inter-satellite links.

Generating one


orbitforge constellation walker \
  --name demo --planes 6 --sats-per-plane 10 \
  --altitude-km 550 --inclination-deg 53 --fov-deg 45 \
  --output demo.json


Generated 'demo' with 60 satellites (6 planes x 10 per plane) -> demo.json

That is a Walker Delta, $53^\circ: 60/6/f$ . The output is a definition, not a trajectory: it fixes where the satellites start. Advancing them through time is propagation.

What altitude actually costs

Altitude is the parameter people reach for first, and its effects pull in opposite directions.

Raising altitude	Effect
Footprint	Grows, so fewer satellites cover the same area
Orbital period	Lengthens, so revisit intervals stretch
Path loss	Grows with the square of range, costing link margin
Drag	Falls sharply, so the orbit lasts longer without maintenance
Radiation	Rises toward the inner Van Allen belt

There is no single best altitude. There is only the altitude that satisfies your coverage, latency, link, and lifetime requirements at once, which is what the design command searches for.

Next steps

Propagation fidelity for how these initial states are advanced through time.
Coverage and revisit for how the resulting geometry is measured.

Question? Give us feedbackDocuments Varaha Constellation Designer main (pre-release)