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Exoplanet Transit Power Budget Planner

Plan a simplified electrical power budget for a exoplanet-transit mission by combining active science, spacecraft bus, and heater loads with design margin.

The calculator also converts the design load into battery energy for a specified eclipse or no-generation interval. It is aimed at early subsystem sizing and trade studies rather than detailed orbital power simulation.

Inputs

W
W
W
%
h
%
Result
—
Design electrical load
Base load—
Margin allocation—
Stored energy required—

1. Enter the payload load
Use the electrical draw expected during the representative science or encounter mode.

2. Add bus and thermal loads
Include avionics, communications support, heaters, and other concurrent loads in the two supporting fields.

3. Set design margin
Use the margin policy appropriate to the project phase.

4. Describe the no-generation interval
Enter the duration the battery must support the design load and the effective delivery efficiency.

5. Review design load and energy
Compare the required watts with generation capability and the watt-hours with usable battery capacity.

Base load = science + bus + heater
Design load = base load × (1 + margin%)
Battery energy = design load × no-generation hours / efficiency

The energy result is usable-delivery adjusted and does not automatically include depth-of-discharge limits, aging, solar-array degradation, or battery reserve policies.

What the result means

The design-load result is the concurrent power demand after applying the entered margin.

Use project-specific duty cycles, end-of-life generation, depth-of-discharge limits, degradation, and thermal conditions for detailed sizing.

Given: 320 W payload, 240 W bus, 90 W heaters, 25% margin, 1.5 h no-generation interval, 90% battery efficiency.

Calculation: Base load = 650 W. Design load = 650 × 1.25 = 812.5 W. Battery energy = 812.5 × 1.5 / 0.90 = 1,354.2 Wh.

Result: The preliminary design point is about 813 W with 1.35 kWh of battery delivery for the modeled interval.

Should communications power be included?

Yes, if communications equipment is active during the modeled operating mode. Put it in the bus load or combine it with another concurrent load.

Is the margin the same as battery reserve?

No. The margin increases the design power load. Battery reserve, allowable depth of discharge, and end-of-life capacity are separate sizing considerations.

Can the no-generation duration be zero?

Yes. The design-load result still works, while required battery energy for that interval becomes zero.

Does this calculate solar-array area?

No. It calculates load and stored-energy demand. Array sizing also depends on solar flux, cell efficiency, pointing, degradation, and operating distance from the Sun.

How should I interpret efficiency?

It represents the fraction of stored battery energy that can be delivered to the load in this simplified calculation. Lower efficiency increases the required stored watt-hours.