Scenario 16 - Cascade
Shift Turnover Notes
Section titled “Shift Turnover Notes”Date: Friday 9 April, 1200 Local (Galway runs UTC in April) Station: GW-01 Galway, Ireland - NATS Europe (planning authority for the network; the only station with the command key) Operator on Duty: You, qualified, solo, both consoles Constellation Ops: Anneke Visser, Rotterdam (REC-PLAYBACK and OBC-WDT-RESET on SAR-1 inside the 12:18 window) SH-02 Shetland: Fiona MacLeod, on the roof with the BUC fan; console yours Customer: Erik Halvorsen, Nordic Maritime Watch (collects on both birds)
Densest window of the week. MERIDIAN-SAR-2 slipped ninety seconds overnight (Rotterdam has not said why) and its Galway window now overlaps the SAR-1 command contact. Morning uplink check at Shetland done at 11:20; nobody has been back to the rack since. Galway TX modem still on 1,465 from Wednesday’s SAR-3 work. GW-01 reference has been clean all week. Plan unbuilt.
Fiona reports a fan alarm coming up on her BUC and is going up to look at it.
- Morning shift (turnover log, 1155)
Fiona (text, 1158):
“Fan alarm on my BUC and I’m going up to look at it, so the console’s yours. Nobody’s touched the rack since the uplink check this morning. SAR-2 moved overnight and Rotterdam hasn’t said why. Your GPSDO’s been fine. Enjoy.”
Order of Work
Section titled “Order of Work”Three problems and eighteen minutes. Triage is ordered by what each problem gates, not by how loud it is.
| Order | Problem | Gates | Why here |
|---|---|---|---|
| 1 | The slipped pass | Which site needs which hardware | The plan decides everything after it |
| 2 | Galway ready to command | The 12:18 window | The window has a time; nothing else does |
| 3 | The Shetland BUC | Nothing today | Shetland’s contact is receive-only. A hot transmit chain on a receive-only site gates no work, but it is still a fault with a right action and a louder wrong one |
| 4 | Fly | Galway commands; Shetland acquires on its own | |
| 5 | Report | Last |
Today’s Contacts (epoch 12:00:00 UTC, 0° horizon)
Section titled “Today’s Contacts (epoch 12:00:00 UTC, 0° horizon)”| Contact ID | Satellite | Horizon | Opens | Closes | Priority |
|---|---|---|---|---|---|
| C-SAR1-SH | MERIDIAN-SAR-1 | Shetland, 56° | 12:15:50 | 12:25:50 | 2 |
| C-SAR1-GW | MERIDIAN-SAR-1 | Galway, 30° - command contact | 12:18:00 | 12:27:40 | 1 |
| C-SAR2-SH | MERIDIAN-SAR-2 | Shetland, 28° - NMW collect | 12:21:20 | 12:30:50 | 1 |
| C-SAR2-GW | MERIDIAN-SAR-2 | Galway, 15° - SLIPPED +90 s | 12:23:30 | 12:32:20 | 2 |
The overnight plan had SAR-2 on Galway after SAR-1. The slip moved its Galway window to 12:23:30, four minutes inside the command contact. The two cannot both sit on Galway, and Shetland already has the same bird at 28° against Galway’s 15°. Priority-1 contacts must be assigned for the plan to validate: the command contact on GW-01, the collect on SH-02, and the slipped Galway half dropped. Dropping a window is a decision the plan records.
Pass Plan
Section titled “Pass Plan”Galway horizon
Section titled “Galway horizon”| Contact | AOS | Rise az | Max Elevation | LOS | Track |
|---|---|---|---|---|---|
| MERIDIAN-SAR-1 | 12:17:59 | 021° | 29.8° at 12:22:49, 728 km | 12:27:35 (az 173°) | Southbound, 9.6 min. The command contact |
| MERIDIAN-SAR-2 | 12:23:32 | 030° | 15.5° at 12:27:58, 1,132 km | 12:32:23 | The slipped half. Dropped |
Shetland horizon
Section titled “Shetland horizon”| Contact | AOS | Rise az | Max Elevation | LOS | Track |
|---|---|---|---|---|---|
| MERIDIAN-SAR-1 | 12:15:54 | 017° | 55.8° at 12:20:53, 468 km | 12:25:49 | One operator: not worked |
| MERIDIAN-SAR-2 | 12:21:16 | 024° | 28.0° at 12:26:05, 763 km | 12:30:51 (az 173°) | Southbound, 9.6 min. The collect, unattended acquisition |
Command window (SAR-1, Galway)
Section titled “Command window (SAR-1, Galway)”| Item | Time |
|---|---|
| Window opens | 12:18:20 |
| Max elevation | 12:22:49 |
| Window closes | 12:27:20 |
Requirements for an ACK: uplink Doppler compensation engaged, command key Valid, command sent inside the window. Ordered: REC-PLAYBACK, then OBC-WDT-RESET. PLD-SAFE is on the console and not ordered.
Expected numbers
Section titled “Expected numbers”| Pass | Decode window | Peak C/N |
|---|---|---|
| SAR-1 from Galway, 30° (beacon, then command) | Beacon on RX analysis from about 12:19 | ~11 dB at 12:22:49 |
| SAR-2 from Shetland, 28° (unattended) | C/N ≥ 8 dB about 12:24:00 to 12:28:10 | ~10.7 dB at 12:26:05 |
Shetland flies its window with nobody at its console: a station armed on program-track with the receiver on the right carrier acquires by itself. What it cannot do is notice a bad number; you check it before 12:30:51, from its console, while it is still up.
The Shetland BUC
Section titled “The Shetland BUC”| Reading | Meaning | Action |
|---|---|---|
| BUC over-temperature, fan alarm, TX modem 1 on air into the BUC, HPA off | The morning uplink check left a carrier driving the BUC. A BUC dissipates heat in proportion to its output; with the fan gone a driven unit draws about 4.3 A (3.1 A is normal) and climbs toward 75 °C, above the 70 °C alarm, as long as a carrier is going in | Carrier off, BUC muted, BUC powered. The current drops to its 2.6 A idle draw at once; the temperature turns down and passes 70 °C within two or three minutes, heading for the mid-50s |
Shetland’s contact today is receive-only. The BUC is the transmit chain and plays no part in it; the receive path is healthy. The alarm gates nothing, and it is still a ticket for the fan and a note for whoever left the carrier up.
The Reference
Section titled “The Reference”GW-01’s GPSDO has been clean all week. If it is not clean during the window, read the panel before doing anything to it.
| Panel reads | It is | Do |
|---|---|---|
| HOLDOVER active, GNSS switch up, zero satellites | A GNSS outage. The oscillator holds the reference to microseconds for tens of minutes; the uplink Doppler pre-compensation does not care | Fly. Leave the switch alone. Confirm re-lock when the signal returns |
| HOLDOVER active, GNSS switch down | An operator error | Switch up |
| Anything, after a power cycle | Ten minutes of warm-up | Do not. The window is gone |
Cycling the switch cannot conjure a satellite. A command goes up on a reference in holdover.
Link Parameters
Section titled “Link Parameters”LNB high-side: IF = LO − RF (13,100 MHz). BUC low-side: RF = IF + LO (12,600 MHz).
| Signal | RF (MHz) | IF (MHz) | Format |
|---|---|---|---|
| SAR-1 imagery downlink | 11,686 | 1,414 | QPSK 3/4, 36 MHz |
| SAR-1 telemetry beacon | 11,711 | 1,389 | CW |
| SAR-1 TT&C uplink | 14,005 | 1,405 | QPSK 3/4, 36 MHz, −7 dBm. GW-01 TX modem is on 1,465 (SAR-3) and must be retuned |
| SAR-2 imagery downlink | 11,730 | 1,370 | QPSK 3/4, 36 MHz |
| SAR-2 telemetry beacon | 11,703 | 1,397 | CW |
Chain order at Galway
Section titled “Chain order at Galway”| Up (inside the window, after the beacon is in) | Down (after both ACKs) |
|---|---|
| 1. TX modem on air, into the muted BUC | 1. HPA output off |
| 2. BUC unmuted | 2. BUC muted |
| 3. HPA output enabled; confirm linear | 3. Carrier off |
Equipment Status at Turnover
Section titled “Equipment Status at Turnover”GW-01 Galway
Section titled “GW-01 Galway”| Equipment | Status | Notes |
|---|---|---|
| 4 m Ku tracker | Powered, manual, parked az 5° / el 3° | Park on az 21° / el 5° for the 12:18 rise |
| TX modem 1 | 1,465 MHz / QPSK 3/4 / −7 dBm, not transmitting | Retune to 1,405 MHz |
| TT&C console | Doppler compensation off | Engage before the window |
| RX modem 1 | 1,414 MHz / 36 MHz / QPSK 3/4 | Stays |
| Spectrum analyzer | 1,414 MHz centre, 60 MHz span | 1,389 MHz, 2 MHz span for the beacon |
| BUC / HPA | Muted, on reference / output disabled | Chain up inside the window |
| GPSDO | Locked, 9 satellites, no holdover | Read it now, so you know what it looked like before the window |
| COMSEC | TX key Valid, RX key Valid | Read both |
| Report | Shift Incident and Impact Report: Contacts, Impact, Actions | Blank |
SH-02 Shetland
Section titled “SH-02 Shetland”| Equipment | Status | Notes |
|---|---|---|
| 4 m Ku tracker | Powered, manual, parked az 5° / el 3° | Program-track with MERIDIAN-SAR-2 as target before 12:21; it acquires on its own |
| TX modem 1 | ON AIR, 1,405 MHz, into the BUC | The drive. Carrier off |
| BUC | Unmuted, powered, over-temperature, fan alarm | Mute; keep powered; watch it come down under 70 °C |
| HPA | Output disabled | Stays off |
| RX modem 1 | 1,414 MHz / 36 MHz / QPSK 3/4 | Retune to 1,370 MHz for SAR-2 |
| GPSDO / LNB | Locked / 13,100 MHz, stable | Confirm |
Qualification Checklist
Section titled “Qualification Checklist”Take the shift (12:00 – 12:05)
Section titled “Take the shift (12:00 – 12:05)”- Handover read; order of work decided
- Plan: C-SAR1-GW on GW-01, C-SAR2-SH on SH-02, slipped half dropped, DECONFLICTED
Galway ready to command (12:05 – 12:11)
Section titled “Galway ready to command (12:05 – 12:11)”- GPS Timing: GPSDO locked, no holdover
- TX chain: TX key Valid; RX analysis: RX key Valid
- TX modem to 1,405 MHz; TT&C: Doppler compensation engaged; RX modem on 1,414; analyzer 1,389 MHz, 2 MHz span
- Tracker parked az 21° / el 5°
Shetland (12:11 – 12:17)
Section titled “Shetland (12:11 – 12:17)”- SH-02 selected; dashboard: the BUC alarm read and its cause named
- TX chain: carrier off, BUC muted, BUC powered; temperature confirmed under 70 °C
- Modem 1 to 1,370 MHz; program-track with MERIDIAN-SAR-2 as target
The command contact (12:18 – 12:28)
Section titled “The command contact (12:18 – 12:28)”- GW-01 selected; program-track MERIDIAN-SAR-1; beacon on RX analysis
- Carrier into the muted BUC; unmute; HPA
- REC-PLAYBACK acknowledged
- GPS Timing read; OBC-WDT-RESET acknowledged before 12:27:20, whatever the reference is doing
Shetland’s pass, Galway’s chain (12:24 – 12:31)
Section titled “Shetland’s pass, Galway’s chain (12:24 – 12:31)”- SH-02 selected before 12:30:51: pedestal program-track locked on SAR-2, modem locked, C/N ≥ 8 dB
- GW-01 selected: HPA off, BUC muted, carrier off
- GPS Timing: GNSS receiving, out of holdover; contacts logged
Close (12:31 – 12:40)
Section titled “Close (12:31 – 12:40)”- SH-02 selected: BUC normal; alarm closed with a cause
- Impact line for Erik; Actions line for maintenance and Rotterdam
End of Briefing
Section titled “End of Briefing”Everything on this shift you have done once: a plan with a conflict, a chain up in order, a command inside a window, a reference that is not what you left it, a site flown with nobody at its console, a fault with a right action and a louder wrong one. What is new is that they arrive together, and the order you take them in is the whole exam.
Qualified means nobody notices. Erik is about to not notice.
Good luck.