On-Board Data Storage & Downlink Throughput Budget
Balance housekeeping telemetry, payload data generation, AX.25/FEC protocol overhead, and FRAM/flash ring-buffer autonomy.
DETERMINISTIC PHYSICS & DATA METHODOLOGY
How This Calculator Works
Source modules: components/lab/v3-tools.tsx, lib/physics/orbit.ts
Balances continuous housekeeping telemetry plus per-orbit payload volume against daily ground-station pass throughput after AX.25 / CCSDS FEC framing overhead, and sizes non-volatile FRAM/NOR ring-buffer autonomy during ground outages.
Governing Equations & Physical Model
D_gen = (R_HK · 86,400) / 1000 + N_orb · D_payload [kB/day]Uses N_orb = 15.15 orbits/day (≈525 km SSO) and decimal kilobytes (1 kB = 8,000 bits on the RF channel).
D_down = (60 · t_contact · R_b · η_proto) / 8000, t_fill = (M_buf · 1024) / D_genAccounts for preamble, sync, AX.25/CSP headers, and FEC parity overhead via protocol efficiency η_proto.
Inputs, Parameters & Units
| Parameter | Unit | Physical definition |
|---|---|---|
| R_HK, D_payload | B/s, kB/orbit | Continuous housekeeping byte rate and science/camera payload volume per orbit. |
| R_b, t_contact | bps, min/day | Radio channel bit rate and usable daily contact time above link-margin mask. |
| η_proto, M_buf | %, MB | Net payload framing efficiency and onboard non-volatile ring-buffer size. |
Assumptions & Validity Limits
- Assumes error-free frame delivery during usable contact minutes; ARQ retransmissions reduce effective η_proto.
- Orbital frequency is fixed at 15.15 orbits/day (525 km circular reference).
Worked Default Reference Case
16 B/s housekeeping plus 45 kB/orbit payload produces 855 kB/day, while 18 min/day at 9600 bps (68% framing efficiency) downlinks 881 kB/day (+27 kB/day positive margin, 2.4 days buffer autonomy).
- Daily data generated
- 855 kB/day
- Daily net downlink
- 881 kB/day (+27 kB/d)
- 2 MB FRAM autonomy
- 2.4 days without contact
- Reference orbit rate
- 15.15 orbits/day