Satellite Solar Panel Degradation Calculator
Overview
Satellites depend on solar arrays to convert sunlight into electrical power for avionics, communications, payloads, and thermal control. Unlike terrestrial systems, space arrays must operate for years without servicing while exposed to radiation, vacuum, and repeated hot/cold transitions. As a result, designers usually work with beginning-of-life (BOL) and end-of-life (EOL) power and include margin to ensure the spacecraft can meet power needs late in the mission.
This calculator provides a simplified estimate of remaining array power versus mission duration using an exponential degradation model. It combines (1) a baseline cell/array aging term, (2) a radiation-related term scaled by an annual dose proxy (krad/year), and (3) a thermal-cycling term scaled by temperature swing amplitude (°C). The intent is screening-level planning and trade studies, not flight certification.
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).
- 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 = kc + kr + kt
Using the simplified linear scaling embedded in this calculator:
- Baseline (technology) term: kc = (Cell Degradation Coefficient)/100
- Radiation term: kr = 0.0008 · F, where F is in krad/year
- Thermal amplitude term: kt = 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.
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:
- kc = 0.5/100 = 0.005
- kr = 0.0008·10 = 0.008
- kt = 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.
| Scenario | Radiation (krad/yr) | Thermal amplitude (°C) | Baseline coeff (%/yr) | Expected EOL trend |
|---|---|---|---|---|
| Lower radiation | Low | Same | Same | Higher remaining power |
| Higher thermal swings | Same | High | Same | Lower remaining power |
| More conservative aging | Same | Same | High | Lower remaining power |
| Shorter mission | Same | Same | Same | Higher remaining power |
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.