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Satellite Link Power Budget Planner

The Satellite Link Power Budget Planner estimates electrical power and energy required during a communications contact. It combines transmitter DC input, modem and RF electronics, antenna or pointing equipment, and other concurrent bus loads, then applies a design margin and contact duration.

The tool is useful for checking whether a satellite power subsystem can support a high-rate downlink or uplink session without exceeding bus capacity or available battery energy. Enter electrical loads rather than RF output power unless you have already converted RF output through transmitter efficiency. The result is a constant-load approximation; actual spacecraft power varies with duty cycle, amplifier back-off, thermal control, attitude, eclipse conditions, and other simultaneous subsystem activity.

Inputs

W
W
W
W
min
%
Result
—
Required contact power incl. margin
Base contact load—
Margin allowance—
Contact energy—

1. Enter transmitter electrical load
Use DC electrical input to the transmitter or amplifier, not RF output power unless they are intentionally the same in your model.

2. Add communications electronics
Include modem, transceiver, frequency conversion, and supporting RF electronics.

3. Add antenna and pointing load
Include gimbals, phased-array electronics, or pointing hardware that is energized during the contact.

4. Enter other bus load
Add spacecraft loads that remain active at the same time.

5. Set duration and margin
Enter usable contact minutes and the design margin applied to simultaneous power demand.

6. Review power and energy
Use watts to check bus capacity and watt-hours to estimate energy drawn during the contact.

Base contact load = Ptx + Pmodem + Pantenna + Pother Required power = Base load × (1 + Margin/100) Contact energy = Required power × Contact minutes / 60

The model assumes all entered loads are simultaneous and constant for the full contact duration.

What the result means

The main result is electrical power capacity required during the link session after design margin is applied.

Battery sizing should also include conversion efficiency, depth-of-discharge limits, eclipse duration, recharge opportunity, aging, and other mission loads.

Given: 220 W transmitter, 45 W modem/RF, 60 W antenna/pointing, 180 W other bus load, 14 minutes, and 20% margin.

Calculation: Base load = 505 W. Required power = 505×1.20 = 606 W. Energy = 606×14/60 = 141.4 Wh.

Result: The contact requires about 606 W of power capacity and 141 Wh of energy under the constant-load assumption.

Should transmitter power be RF output or DC input?

Use electrical input power for a spacecraft power budget. If you only know RF output, convert it using amplifier efficiency before entering it.

Does antenna gain affect this power calculation?

Not directly. Antenna gain belongs in the RF link budget, although higher-gain active or steerable antennas may require additional electrical power that should be entered as a load.

Can I include eclipse operation?

Yes, the load math still applies. Battery and generation analysis must separately determine whether the required energy is available during eclipse.

Why include other bus load?

Communications rarely operate alone. Adding concurrent spacecraft loads avoids understating total bus demand during the contact.

How is this different from the signal budget planner?

The power budget tracks spacecraft electrical watts and watt-hours; the signal budget tracks RF gains, losses, received power, and link margin in dB.