Spacecraft Thermal Balance in Orbit (2D)

Orbit & Surface

Orbital altitude 400 km

Absorptivity α 0.30

Emissivity ε 0.85

Thermal mass 40 kJ/K

Live Readouts

☀ In sunlight

Surface temperature

288.0 K

Temperature (°C)

14.9 °C

Absorbed power

0 W

Radiated power

0 W

Orbital period

92.5 min

Eclipse fraction

36%

How it works (2D model)

This 2D companion uses the exact same orbital energy balance as the 3D version, viewed top-down instead of in a perspective camera. A satellite in low orbit swings between direct sunlight and the planet's shadow every orbit; its surface temperature is set by the balance between absorbed solar power and radiated thermal power:

P_abs = α · S · A_cross   (0 while eclipsed)
P_rad = ε · σ · A_total · T⁴
C · dT/dt = P_abs − P_rad

where S = 1361 W/m² is the solar constant, σ = 5.67×10⁻⁸ W/m²K⁴ is the Stefan–Boltzmann constant, α is absorptivity, ε is emissivity, A_cross and A_total are the sunlit cross-section and total radiating area of a 1 m-class spherical satellite, and C is the object's thermal mass.

Orbital altitude — sets the orbital period via Kepler's third law and the fraction of each orbit spent in the planet's cylindrical shadow (eclipse), shown here as the dark wedge behind the planet.
Absorptivity α / Emissivity ε — surface coatings change these independently; a low α/ε ratio (white paint) stays cooler, a high ratio (bare metal) runs hotter.
Thermal mass — a heavier or higher-heat-capacity structure smooths out the temperature swing between eclipse and sunlight; a light structure swings almost instantly.

The satellite marker's own colour tracks its live temperature (blue = cold, red = warm), the same encoding as the 3D scene. A scrolling chart of the temperature history makes the eclipse-driven oscillation easy to read at a glance. Drag to pan the orbit view and scroll/pinch to zoom.

Satellite Sun direction Orbit path

Temperature history

drag to pan · scroll to zoom