Satellite Solar Panel Degradation Calculator

How to use this calculator

1. Enter beginning-of-life array power and the power the spacecraft must still deliver at end of mission.
2. Set mission duration, annual radiation dose proxy, thermal cycle amplitude, and the baseline annual cell degradation coefficient.
3. Review the projected EOL output, retained capacity, power margin, and estimated year when output falls below the required load.
4. Use the breakdown to see whether baseline aging, radiation, or thermal stress is dominating the simplified decay rate.

Inputs (what they mean)

• Initial Array Power (W): your BOL array power under the conditions you consider “initial” (often at beginning of mission, at a specified incidence angle and temperature).
• Required EOL Load (W): the electrical power the spacecraft must still support at end of mission, including payload, bus, heater, battery-charge, and regulator margins you want to reserve.
• Mission Duration (years): total time the array must operate. If you have months, divide by 12.
• Radiation Flux (krad/year): an annualized dose proxy. In practice, total ionizing dose depends strongly on orbit (LEO vs MEO vs GEO), shielding thickness, solar cycle, and trapped belt environment.
• Thermal Cycle Amplitude (°C): an approximate peak-to-peak temperature swing experienced by the array during eclipse/sunlight transitions (or other operational cycles).
• Cell Degradation Coefficient (%/year): a baseline annual degradation rate representing technology aging and other non-modeled effects. If you have vendor EOL data, you can back-calculate an effective annual coefficient and use it here.

Model and formulas

We model remaining power as an exponential decay from the initial value:

Where:

• P(t) is the estimated power after t years (W).
• P₀ is the initial array power (W).
• k is the combined degradation coefficient (1/year).

The combined coefficient is the sum of three components:

k = k_c + k_r + k_t

Using the simplified linear scaling embedded in this calculator:

• Baseline (technology) term: k_c = (Cell Degradation Coefficient)/100
• Radiation term: k_r = 0.0008 · F, where F is in krad/year
• Thermal amplitude term: k_t = 0.0001 · A, where A is in °C

So the total becomes:

k = (c/100) + 0.0008·F + 0.0001·A

with c in %/year, F in krad/year, and A in °C.

Derived outputs

• Remaining Power (W): P(t).
• Percent Remaining (%): 100 · P(t)/P₀.
• Total Degradation (%): 100 − Percent Remaining.
• EOL Power Margin: remaining power minus required EOL load.
• Load-crossing year: the estimated year when the simplified degradation curve falls below the required load, if that crossing occurs.

How to interpret the results

The output is an estimate of average electrical power capability at the end of the mission relative to the initial power you entered. Use it as a first-pass EOL factor for:

• power budget sanity checks (can the spacecraft close power at EOL?),
• trades between mission duration and array sizing,
• sensitivity studies (e.g., how much does assumed radiation environment move EOL power?).

If the calculator predicts a low percent remaining, typical mitigations include increasing array area, improving shielding/cover glass, selecting more radiation-tolerant cell technology, or revisiting operational temperature extremes.

Worked example

Suppose:

• P₀ = 5000 W
• t = 5 years
• F = 10 krad/year
• A = 80 °C
• c = 0.5 %/year

Compute the coefficient:

• k_c = 0.5/100 = 0.005
• k_r = 0.0008·10 = 0.008
• k_t = 0.0001·80 = 0.008
• k = 0.005 + 0.008 + 0.008 = 0.021 1/year

Remaining power:

P(5) = 5000 · e^−0.021·5 ≈ 5000 · e^−0.105 ≈ 4500 W (approx.)

Percent remaining is about 90%, meaning total degradation over the mission is about 10% under these simplified assumptions.

Comparison: how different assumptions change EOL power

The table below illustrates directional effects (holding P₀ and mission duration fixed). Your actual environment and hardware can produce different sensitivities.

Assumptions & limitations

• Illustrative coefficients: The 0.0008 (radiation) and 0.0001 (thermal amplitude) factors are simple empirical placeholders to provide a tunable combined decay rate. For real missions, calibrate coefficients to test data, vendor curves, or a radiation/thermal/mechanical model.
• Orbit/environment not explicitly modeled: Radiation effects depend on orbit, inclination, solar cycle, trapped belts, shielding, cover glass, and cell type. A single “krad/year” input cannot capture spectrum and displacement damage details.
• Thermal cycling frequency ignored: The model uses amplitude only, not number of cycles, dwell times, gradients, or panel-level mechanical design—important drivers of fatigue and cracking.
• Single exponential decay: Real degradation can be non-linear (early-life drop, step changes from events, annealing, or end-of-life acceleration). This tool assumes a smooth trend.
• No attitude/incidence effects: Changes in pointing, seasonal beta angle, cosine losses, eclipse duration, and contamination are not included unless baked into your initial power and chosen coefficients.
• Electrical architecture not included: String-level failures, bypass diode behavior, partial shading, regulator limits, and harness losses can affect delivered bus power beyond cell degradation alone.
• Use for planning, not qualification: Treat outputs as rough-order estimates and apply appropriate design margin and verification for mission-critical decisions.