Communication / Ground Link
Data Rate × Contact Time
Estimate how much data can be downlinked in one or more passes by combining data rate, contact duration, and number of passes against a payload data volume.
- Time estimate
- 20–25 min
- Complexity
- developing
- Maturity
- pilot ready
- Simulator readiness
- implemented
- Software available now
- Implemented — interactive data-rate × contact-time teaching lab at `/twin/learn/activities/comm_data_rate_contact_budget`. Not a protocol-accurate throughput simulator, no real licensed link planning.
Student path
- Pick a data-rate preset, contact duration, and number of passes per day.
- Pick a payload data volume target — read total downlinkable data and utilization.
- Identify capacity status (within / tight / over) and any backlog.
- Name one mitigation if backlog exists, then copy/export evidence.
Learning outcomes
Student can compute a teaching-grade data budget (data rate × contact time × passes) and identify when payload data exceeds available downlink.
- Compute downlinkable data as data rate × contact time × passes.
- Compare downlinkable data to a payload data volume and identify backlog.
- Propose one mitigation when payload data exceeds downlink capacity.
Concept primer
Estimate how much data can be downlinked in one or more passes by combining data rate, contact duration, and number of passes against a payload data volume.
Open the Data Rate × Contact Time lab at `/twin/learn/activities/comm_data_rate_contact_budget` — browser-local teaching estimate (not protocol-accurate throughput).
Compute downlinked MB for one pass at 9.6 kbps for 8 minutes, 100 kbps for 8 minutes, and 1 Mbps for 8 minutes (round numbers; teaching model).
Interactive lab
Teaching-grade software activity slot — not a flight simulator or certified propagator.
Interactive lab
Data rate × contact time (teaching)
Combine data rate, contact duration, and number of passes per day to estimate downlinkable data, then compare to a payload data volume. Teaching estimate, not a protocol-accurate throughput simulator.
Downlink capacity (teaching estimate)
- Data rate
- 19.2 kbps
- Per pass downlink
- 0.8 MB
- Per day downlink
- 3.4 MB
- Payload demand
- 50 MB / day
Capacity status
Over capacity
Utilization (payload vs capacity): 999%
Backlog: 46.6 MB / day not downlinked.
Payload exceeds daily downlink capacity — choose a higher data-rate radio (cost: mass/power), reduce capture cadence, schedule more passes, or ship onboard compression.
Local self-check
Assessment (practice only)
Use this as a self-check and discussion starter. It is local-only and not a grade.
Optional: attaches a local summary (completed / quick checks / checklist count).
Quick check
Multiple choice self-check
This is a local self-check to support discussion. It is not a grade.
Quick check: Doubling the data rate while keeping contact time the same…
Quick check: If payload data per day exceeds total downlinkable data per day…
Discussion prompt
Short answer (local only)
Write notes for yourself or your group. Nothing is submitted.
Short answer: Name one mitigation when payload data exceeds downlink (operations) and one (design).
Checklist
Local checklist self-check
Use this to verify you covered key ideas. Nothing is submitted.
Checklist: Data-rate budget readiness (self-check)
0 / 4 checked
Local summary
Assessment summary (practice only)
Completion
0 / 4 sections complete
Quick checks
0 / 2 correct
Shown only to support self-check.
Checklist
0 / 4 items checked
Reminder
Local-only practice summary. Not a grade and not submitted anywhere.
What this preview is / is not
Assessment engine v0 boundary note
- Student view (local practice): use this as a self-check and discussion starter.
- Local-only preview/practice: your answers are not submitted.
- No backend, no accounts, no roster, and no LMS integration.
- Not a grade. No credential or official scoring is implied.
- Teacher visibility into student answers is not implemented in MVPF8.
- Evidence runtime engine arrives in Phase 9 (not in this preview).
Capture
Evidence capture (local-only)
Capture what you did, what changed, what you observed, and how you explain it. This stays in your browser unless you copy/share it manually.
Selected inputs
- Data rate preset: UHF telemetry (19.2 kbps)
- Contact duration per pass: 6 min
- Passes per day: 4
- Payload data per day: 50 MB
Generated outputs
- Per-pass downlinkable data: 0.8 MB
- Per-day downlinkable data: 3.4 MB
- Utilization (payload vs capacity): 999%
- Backlog (per day): 46.6 MB
- Capacity status: over_capacity
- Mitigation: Payload exceeds daily downlink capacity — choose a higher data-rate radio (cost: mass/power), reduce capture cadence, schedule more passes, or ship onboard compression.
Checklist
Evidence checklist
0/4 checked
Evidence artifact (local-only)
Data Rate × Contact Time
Captured: 2026-05-16T07:38:33.093Z · Level: high_school · Track: communication_ground_link
Summary
Copyable class summary
Copy a readable summary for class notes, or copy JSON for a structured record. Local-only: nothing is submitted.
Evidence artifact (v1) Activity: Data Rate × Contact Time Track: communication_ground_link Learner level: high_school Captured: 2026-05-16T07:38:33.093Z Mission brief: Teaching data budget combining data rate, contact duration, and number of passes (not protocol-accurate throughput). Selected inputs: - Data rate preset: UHF telemetry (19.2 kbps) - Contact duration per pass: 6 min - Passes per day: 4 - Payload data per day: 50 MB Generated outputs: - Per-pass downlinkable data: 0.8 MB - Per-day downlinkable data: 3.4 MB - Utilization (payload vs capacity): 999% - Backlog (per day): 46.6 MB - Capacity status: over_capacity - Mitigation: Payload exceeds daily downlink capacity — choose a higher data-rate radio (cost: mass/power), reduce capture cadence, schedule more passes, or ship onboard compression. Checklist: - [ ] Selected data rate, contact duration, passes, and payload volume - [ ] Read total downlinkable data and identified backlog status - [ ] Named one mitigation if backlog existed - [ ] Treated this as a teaching estimate, not protocol-accurate throughput Observations: (not provided) Reflection: Mitigation I would try first if my payload demand exceeded my downlink budget. Model boundary note: Local-only teaching model — not a certified RF link budget, not ITU/regulatory analysis, not licensed radio operations, not real satellite command, no SDR or remote hardware. Evidence is not submitted anywhere and is not a grade. Policy reminder: - Local-only capture. Not submitted anywhere. Not a grade.
Evidence capture
Expected outputs learners should be able to show after the lab (Phase 9 evidence engine preview available).
- Data rate, contact duration, passes, and payload volume chosen
- Total downlinkable data and backlog status (within capacity / over capacity)
- One mitigation if backlog exists (lower rate of capture, schedule more passes, prioritise data, etc.)
- Local self-check summary and copied evidence text
Reflection
Pick a data rate preset, contact duration, number of passes, and a payload data volume; read total downlinkable data, backlog, and a mitigation suggestion if over capacity.
Responses are not persisted in this preview unless a specific activity component adds storage later.
Assessment / quick check
Why can a CubeSat with a fast radio still fail to downlink all its payload data in a day?
Teacher notes
Reinforce that data rate alone is not enough — contact time and number of passes per day are the real bottleneck for many CubeSat missions.
Teacher use
Stress that downlinkable data = data rate × contact time × passes. Push teams to compare a fast radio + few passes vs a slow radio + many passes; both can be optimal depending on ground-station coverage. Teaching estimate — not a protocol-accurate throughput simulator.
Next activity
Suggested progression from the mission learning path. Links avoid missing activity routes.