Scenario 4 - Keys to the Bird
Shift Turnover Notes
Section titled “Shift Turnover Notes”Date: Thursday, 1345 Local (Galway runs UTC in March) Station: GW-01 Galway, Ireland - NATS Europe Operator on Duty: You Site Lead: Charlie Brooks (on-site, front office) Constellation Ops Contact: Anneke Visser, MERIDIAN Constellation Operations (Rotterdam)
Clean uplink yesterday, so Rotterdam has given us a real one today: safe-mode the payload before the next imaging block. There is a complication, which is that the scheduled key rotation was booked weeks ago and has, naturally, arrived in the middle of your only pass.
The bird authenticates every command. A key that is mid-rotation is not a key. Finish the rotation before the pass, then send. And leave the zeroize switch exactly where it is.
- Charlie (text, 1344)
Two Keys
Section titled “Two Keys”| Key | Where | What it does | State at turnover | Today |
|---|---|---|---|---|
| Command-link authentication key | TT&C console, COMSEC panel | Signs every command so the spacecraft can prove who sent it. requireValidKey is on: Pending Rotation is a NAK. |
Pending Rotation (new material loaded, not active) | Rotate it, in two steps, before the pass |
| Traffic key | Payload crypto panels (TX Chain and RX Analysis) | AES-256-GCM, symmetric. Encrypts what you send, decrypts what comes down, verifies the auth tag. | Valid, 62 days to expiry | Rotterdam rotates the fleet traffic key on its own schedule. Watch it after the pass. |
Different custody, different schedules. People confuse them constantly. Read both before you touch either.
Command Request
Section titled “Command Request”Ref: MER-OPS-2027-0318 From: A. Visser, MERIDIAN Constellation Operations To: GW-01 Galway Priority: Required before next imaging block
GW-01: uplink PLD-SAFE to MERIDIAN-SAR-1 on the 14:03 UTC pass. The payload enters its next imaging block after your LOS; we need it safed before then for a thermal check.
Our records show your station’s command key is in its scheduled rotation window today. Please confirm the rotation is complete and the key reads Valid before you send - an unauthenticated PLD-SAFE will be rejected and we will not get a second window in time.
Separately: the fleet traffic key rolls at 14:11 UTC on our schedule. New material is on your console.
- Anneke
| Command | Mnemonic | Tasked This Pass |
|---|---|---|
| Payload to safe mode | PLD-SAFE | Yes |
| Start recorder playback | REC-PLAYBACK | No |
| Reset OBC watchdog | OBC-WDT-RESET | No |
Pass Plan and Command Window (5° mask, epoch 13:45:00 UTC)
Section titled “Pass Plan and Command Window (5° mask, epoch 13:45:00 UTC)”| Item | Time |
|---|---|
| MERIDIAN-SAR-1 AOS | 14:03:10 |
| Command window opens | 14:03:40 |
| Max elevation (28°) | 14:06:45 |
| Command window closes | 14:10:00 |
| MERIDIAN-SAR-1 LOS | 14:10:18 |
| Fleet traffic key rotation (Rotterdam) | 14:11:00 |
| MERIDIAN-SAR-2 AOS / max el / LOS | 14:18:42 / 25° at 14:22:10 / 14:25:40 |
SAR-2 is not tasked for commanding. It is available, optionally, to prove the new traffic key on live frames (RX modem 1 to 1,370 MHz).
Uplink Plan
Section titled “Uplink Plan”Unchanged from yesterday. BUC low-side, RF = IF + LO (12,600 MHz LO). TX modem 1 is on 1,405 MHz. Uplink Doppler ±325 kHz, pre-compensated at the console.
| Path | IF (MHz) | RF (MHz) | Format |
|---|---|---|---|
| SAR-1 telecommand uplink | 1,405 | 14,005 | QPSK 3/4, 36 MHz, −7 dBm modem |
| SAR-1 telemetry beacon (down) | 1,389 | 11,711 | CW |
| SAR-2 imagery downlink | 1,370 | 11,730 | QPSK 3/4, 36 MHz |
Transmit Chain Status
Section titled “Transmit Chain Status”| Equipment | Status | Notes |
|---|---|---|
| TX modem 1 | 1,405 MHz / 36 MHz / QPSK 3/4 / −7 dBm | Powered, not transmitting |
| BUC | 12,600 MHz LO, reference locked, gain 23 dB, muted | As yesterday left it |
| HPA | Powered, output disabled | 10 dB back-off |
| Payload crypto | AES-256-GCM ACTIVE both ways, key Valid | Re-key control on the TX Chain payload panel: Load New Key |
| 4 m Ku tracker | Manual, parked az 5° / el 3° | Program-track available |
| GPSDO | Locked, 9 satellites | Disciplined |
Chain order is the same three steps up (carrier into the muted BUC, unmute, HPA) and the mirror down. Yesterday’s rule; today it is assumed.
TT&C Console Reference
Section titled “TT&C Console Reference”| Display | Meaning |
|---|---|
| Key badge | Valid / Pending Rotation / Zeroized |
| Initiate Key Rotation | Marks the current key Pending Rotation and stages the new material |
| Confirm Key Rotation | Completes the handshake; the key reads Valid |
| Zeroize (armed-then-fire) | Destroys the key material. Not part of any rotation. A zeroized station cannot command anything until re-keyed by Rotterdam, and that does not happen inside a seven-minute pass. |
| NAK: key invalid | Sent under a key that is not Valid |
Commanding Checklist
Section titled “Commanding Checklist”Before the Pass (13:45 – 14:03)
Section titled “Before the Pass (13:45 – 14:03)”- TX Chain and RX Analysis payload panels: encryption ACTIVE both ways, traffic key Valid
- TT&C: Initiate Key Rotation, then Confirm; key badge reads Valid
- GPS Timing: GPSDO locked; TX Chain: BUC on external reference
- Pass Schedule: window 14:03:40 – 14:10:00 confirmed
- TT&C: uplink Doppler compensation engaged
- Chain up: carrier into muted BUC; unmute; HPA enabled, not overdriven
- Antenna: program-track on MERIDIAN-SAR-1; beacon on RX analysis
In the Window (14:03:40 – 14:10:00)
Section titled “In the Window (14:03:40 – 14:10:00)”- PLD-SAFE sent; ACK in Command History
After LOS
Section titled “After LOS”- Chain down: HPA off, BUC muted, carrier off
- RX Analysis payload panel at 14:11: decrypt failing, auth tag unverified, traffic key Mismatch. Diagnose before touching anything.
- TX Chain payload panel: Load New Key; both panels read Valid
- Optional: SAR-2 at 14:18 on 1,370 MHz to prove the new traffic key on live frames
- COMSEC log: both keys, both events, with times
End of Briefing
Section titled “End of Briefing”A rotation you complete is hygiene. A rotation the far end completes without you is a mismatch, and the first you hear of it is a decoder that has stopped understanding the spacecraft. Today has one of each.
Finish the command-key rotation before the window. Get the ACK. Then read the traffic key before you touch it.
Good luck.