CubeSTEM Digital Twin · Track 4
Track 4 — Communication / Ground Link
A four-session mini-course: line-of-sight contact basics → data rate × contact time budget → simplified link margin trade-offs → command/telemetry flow with priorities and retries.
Local-only mini-course: no account, no submissions, no gradebook. Teaching-grade estimates — not a certified RF link budget, not ITU/regulatory analysis, not licensed radio operations, no real satellite command, no SDR or remote hardware.
What this mini-course teaches
Understand line of sight, contact time, simplified link margin trade-offs, and command/telemetry flow — with honest teaching-grade models (not RF certification, not real satellite command).
Mini-course flow
Four sessions, one communication story
Four sessions, one communication story: start with line-of-sight contact basics, build a daily downlink budget, reason about simplified link-margin trade-offs, then trace a command and telemetry flow through a short, lossy pass. Evidence and self-checks are local-only — copy, export, or screenshot to share.
Recommended pacing: one session per activity. Use the "Next →" link at the bottom of each activity page to continue in order. After Session 4 the mini-course bridges toward Attitude Control (Track 5) or the Curriculum Map.
Session 1
Line-of-Sight Communication
Time estimate: 20–25 min
Learning goal: Student can explain why ground-station contact depends on satellite visibility above the horizon and on a minimum elevation angle.
Expected evidence (local)
- Ground station + pass scenario + minimum elevation chosen
- Visible / not visible result with reason (below horizon / low elevation / good pass)
- Approximate contact-duration label
Session 2
Data Rate × Contact Time
Time estimate: 20–25 min
Learning goal: Student can compute a teaching-grade data budget (data rate × contact time × passes) and identify when payload data exceeds available downlink.
Expected evidence (local)
- 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.)
Session 3
Link Margin Trade-off
Time estimate: 25–30 min
Learning goal: Student can read a teaching-grade margin badge (safe / weak / failed) and explain one trade-off and one improvement (teaching-grade only).
Expected evidence (local)
- Selected distance, transmit power, antenna gain, data rate, and noise preset
- Teaching margin score with safe / weak / failed badge
- One trade-off explanation in plain language
Session 4
Command / Telemetry Flow
Time estimate: 20–30 min
Learning goal: Student can explain what gets sent first when contact time is short and what happens to lost packets in a teaching priority queue (no real radio).
Expected evidence (local)
- Selected command type, telemetry priority, packet loss / retry, and payload queue
- Command-response timeline and ordered priority queue result
- What gets sent first and what is dropped or deferred
Teacher plan
Track 4 — Communication / Ground Link
A complete four-session mini-course on the communication systems layer between budgets (Track 3) and attitude control (Track 5). Keep language humble throughout: teaching-grade estimates only — not a certified RF link budget, not ITU/regulatory analysis, not licensed radio operations, no real satellite command, no SDR, no remote hardware. Local-only — no submissions, no gradebook, no teacher visibility unless artifacts are shared manually.
45-minute essentials
45 min
- 5 min: boundaries + brief recap of Track 3 budgets → why comms matters next.
- 15 min: Session 1 — Line-of-Sight Communication (visibility + minimum elevation).
- 15 min: Session 2 — Data Rate × Contact Time (daily downlink capacity + backlog).
- 10 min: team reflection — copy/export one evidence artifact each before finishing.
90-minute workshop
90 min
- 20 min: Sessions 1–2 in sequence, then compare team downlink budgets.
- 25 min: Session 3 — Link Margin Trade-off, group debate on which knob matters most.
- 30 min: Session 4 — Command / Telemetry Flow, priority queues, short+lossy pass.
- 15 min: tie-back to Track 3 budgets and preview Track 5 attitude control framing.
Half-day studio
3+ hrs
- Run all four sessions in order with facilitated team pivots between sessions.
- Optional: open the Mission Design Lab and point to the qualitative comms labels.
- Portfolio goal: one exported evidence artifact per team per session (copy/export, no upload).
- Wrap with the 'After Track 4' bridge — Attitude Control overview when available, otherwise Curriculum Map.
Misconceptions bank
- Ground-station contact is not continuous — short passes are normal for LEO CubeSats.
- Higher minimum elevation reduces, not increases, usable contact time.
- Faster radios alone don’t solve a backlog — passes per day and contact duration matter more.
- Pushing data rate too high reduces link margin; trade-offs are real, not free.
- Uplink and downlink are different — small commands up, larger data down.
- Browser labs are teaching-grade — not RF certification, not real satellite command.
Bridge — Mission Realism Lab
Try packet errors, link margin, and retry behavior in Mission Realism Lab.
After Track 4
Bridge students into Attitude Control & Pointing (Track 5) next. The Track 5 dedicated overview hub has not yet shipped, so the Curriculum Map is the safe destination until it does. Evidence stays local — no submissions, no gradebook, nothing to collect unless students share artifacts manually.
Student path
What to do, step by step
This is a guided path, not a submission system. Your evidence and self-check stay in your browser unless you copy/export or screenshot it to share manually.
Tip: after each session, open the Evidence panel and copy/export your artifact (text or JSON) before moving on. Four sessions cover the full mini-course — you don't need anything outside the browser.
Step 1
Line-of-Sight Communication
Time estimate: 20–25 min
- Pick a ground station preset, satellite pass scenario, and minimum elevation angle.
- Read the visible / not visible result and the reason (below horizon / low elevation / good pass).
- Note the approximate contact-duration label for that pass.
- Capture evidence: settings + visibility + reason + duration label.
Step 2
Data Rate × Contact Time
Time estimate: 20–25 min
- Pick a data-rate preset, contact duration, number of passes, and a payload data volume.
- Read total downlinkable data and the backlog status (within capacity / over capacity).
- Name one mitigation if backlog exists (rate, duty, more passes, prioritisation).
- Capture evidence: settings + total downlinkable data + backlog + mitigation.
Step 3
Link Margin Trade-off
Time estimate: 25–30 min
- Pick a distance/orbit preset, Tx power, antenna gain, data rate, and noise/interference preset.
- Read the teaching margin score and safe / weak / failed badge.
- Identify one trade-off and one suggested improvement.
- Capture evidence: settings + margin score + trade-off + improvement.
Step 4
Command / Telemetry Flow
Time estimate: 20–30 min
- Pick a command type, telemetry priority, packet loss / retry profile, and payload data queue.
- Read the command-response timeline and what gets sent first under prioritisation.
- Identify what is dropped or deferred when contact time is short and loss is non-zero.
- Capture evidence: settings + timeline + priority result + reflection sentence.
Bridge — Mission Realism Lab
Try packet errors, link margin, and retry behavior in Mission Realism Lab.
After Track 4
You've completed the Track 4 Communication / Ground Link mini-course. Continue toward Track 5 — Attitude Control & Pointing. The Track 5 hub has not yet shipped, so the Curriculum Map is the safe next destination. Labs are teaching-grade only — not a certified link budget, not real satellite command, no SDR.
Evidence checklist
What to capture across all four sessions
Evidence artifacts are local-only — there is no submission system or teacher-visibility workflow. Copy/export (text or JSON) or screenshot to share manually with your teacher or team.
Classroom tip: after each session, copy/export one artifact per team and paste into a shared document or slide deck. Keeps evidence lightweight and requires no accounts.
Line-of-Sight Communication
⏱ 20–25 min
- Ground station + pass scenario + minimum elevation chosen
- Visible / not visible result with reason (below horizon / low elevation / good pass)
- Approximate contact-duration label
- Local self-check summary and copied evidence text
Reflection prompt: Why does a ground station only see a CubeSat for a short window each pass, and why does minimum elevation matter?
Data Rate × Contact Time
⏱ 20–25 min
- 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 prompt: Why can a CubeSat with a fast radio still fail to downlink all its payload data in a day?
Link Margin Trade-off
⏱ 25–30 min
- Selected distance, transmit power, antenna gain, data rate, and noise preset
- Teaching margin score with safe / weak / failed badge
- One trade-off explanation in plain language
- One suggested improvement and the local self-check summary
Reflection prompt: If the teaching margin is weak, name two changes (one operational, one design) that could push it back to safe — and a cost or downside of each.
Command / Telemetry Flow
⏱ 20–30 min
- Selected command type, telemetry priority, packet loss / retry, and payload queue
- Command-response timeline and ordered priority queue result
- What gets sent first and what is dropped or deferred
- Local self-check summary and copied evidence text
Reflection prompt: When contact time is short and packet loss is non-zero, why must operators set priorities for what gets sent first?
Boundary reminder: teaching-grade communication models — not a certified RF link budget, not ITU/regulatory analysis, not licensed radio operations, no real satellite command, no SDR or remote hardware. Evidence is local-only.
Assessment map
Self-check prompts (not a grade)
Local-only practice — no gradebook, no teacher visibility unless learners share artifacts manually. Use the prompts and misconception cards below as discussion starters, debrief anchors, and formative reflection during and after each session.
Line-of-Sight Communication
Open →Prompt: Why does a ground station only see a CubeSat for a short window each pass, and why does minimum elevation matter?
Common misconceptions
- “Ground stations always see the satellite.” (Contact requires line of sight + minimum elevation.)
- “This lab predicts real passes.” (It is teaching geometry, not orbit propagation.)
Data Rate × Contact Time
Open →Prompt: Why can a CubeSat with a fast radio still fail to downlink all its payload data in a day?
Common misconceptions
- “A faster radio fixes any backlog.” (Contact time and passes per day are usually the bottleneck.)
- “We can downlink unlimited data per day.” (Data budgets are finite.)
Link Margin Trade-off
Open →Prompt: If the teaching margin is weak, name two changes (one operational, one design) that could push it back to safe — and a cost or downside of each.
Common misconceptions
- “This is a certified link budget.” (It is a qualitative teaching estimator only.)
- “Higher data rate is always free.” (Higher rate usually costs link margin.)
Command / Telemetry Flow
Open →Prompt: When contact time is short and packet loss is non-zero, why must operators set priorities for what gets sent first?
Common misconceptions
- “Uplink and downlink are the same.” (Uplink is small commands; downlink is bigger telemetry/data.)
- “This sends real commands.” (No real radio, no real satellite command — teaching flow only.)
Teaching-grade boundary
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.
Not a certified RF link budget. Not ITU/regulatory or licensed-radio analysis. No real satellite command, no SDR, no remote hardware control. Track 5 (Attitude Control) has no dedicated overview hub yet — the Curriculum Map is the safe bridge until that hub ships.
Track 4 — four-session mini-course
All four sessions are interactive and available now. Complete them in order to cover the full Communication / Ground Link arc from line-of-sight basics through command/telemetry flow.
- Line-of-Sight CommunicationCore — Decide whether a satellite is visible from a chosen ground station above a minimum elevation, and read a teaching-grade contact-duration label.
- Data Rate × Contact TimeCore — 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.
- Link Margin Trade-offCore — Use a simplified link-margin model to see how distance, transmit power, antenna gain, data rate, and noise/interference shift a teaching margin score.
- Command / Telemetry FlowCore — Distinguish uplink commands, downlink telemetry, payload data, packet loss / retry, and prioritization with a teaching-grade flow model.
Next step after Track 4
Attitude Control & Pointing — or curriculum map
Track 5 covers Attitude Control & Pointing — ADCS reasoning, reaction wheels, and pointing error trade-offs. The dedicated Track 5 hub has not shipped yet; the Curriculum Map is the safe bridge until it does.