Scenario 8 - Night Passes
Shift Turnover Notes
Section titled “Shift Turnover Notes”Date: Tuesday 16 March, 0015 Local (Galway runs UTC in March) Station: GW-01 Galway, Ireland - NATS Europe (planning authority tonight) Operator on Duty: You, unassisted Site Lead: Charlie Brooks (at home; phone on, expects it not to ring) SH-02 Shetland: Fiona MacLeod, on console until 0100, then remote from GW-01 - yours
Evening shift left it tidy. SAR-1 has a 40 degree pass at 00:31 and it is the best geometry this station has seen. Rotation is pending on the command key. Rotterdam wants REC-PLAYBACK on the pass. Contact plan for the night is not built, and after Fiona goes off at one the Shetland console is yours as well.
This is the qualification shift. Everything on it you have done once. Nobody is going to prompt you to do it again.
- Charlie (text, 2340)
Fiona (text, 0017):
“On console till one. I’ll take whatever the plan gives me before then and after that SH-02 is yours, remote. The GNSS antenna up here has been flaky in the wind all week; if it drops out you know what holdover looks like. Don’t ring unless the building’s on fire.”
Dana Torres (text, 0019):
“Heard from Charlie that tonight’s the one. Same as Vermont: nobody’s coming, and that’s the point. You’ve got this.”
Tonight’s Contacts (epoch 00:15:00 UTC, 5° mask)
Section titled “Tonight’s Contacts (epoch 00:15:00 UTC, 5° mask)”| Contact ID | Satellite | Horizon | AOS | Rise az | Max El | LOS | Priority |
|---|---|---|---|---|---|---|---|
| N-SAR1-GW | MERIDIAN-SAR-1 | Galway | 00:31:19 | 184° | 40.4° at 00:35:03, 581 km | 00:38:49 | 1 |
| N-SAR1-SH | MERIDIAN-SAR-1 | Shetland | 00:33:31 | 213° | 17.0° at 00:36:43, 1,071 km | 00:39:56 | 1 |
| N-SAR2-SH | MERIDIAN-SAR-2 | Shetland | 02:54:39 | 042° | 13.4° at 02:57:34, 1,233 km | 03:00:27 | 2 |
| N-SAR2-GW | MERIDIAN-SAR-2 | Galway | 04:27:31 | 018° | 73.1° at 04:31:23, 408 km | 04:35:12 | 1 |
| N-SAR2-SH-2 | MERIDIAN-SAR-2 | Shetland | 04:25:31 | 016° | 72.5° at 04:29:23, 410 km | 04:33:13 | 3 |
The plan requires priority 2 and above. Two pairs overlap and cannot sit on one site: the SAR-1 pair at 00:33, and the SAR-2 pair at 04:27, which is the same orbit seen from both sites four minutes apart. The 04:25 Shetland overhead is priority 3: Fiona is off shift, one operator cannot fly both sites through the same four minutes, and the 73° Galway pass is the stronger one to fly alone. Dropping it is a decision the plan records.
SAR-2 at 02:54 is a 13° Shetland pass that Galway sees only as a 5.6° graze. It goes to SH-02, and you fly it from here.
The gaps are two and a half hours, then ninety minutes. The scheduler will offer to skip ahead once each contact is worked and logged; mission-elapsed time advances with the skip, so the plan, the faults and the command window stay aligned with the sky.
Who Flies What
Section titled “Who Flies What”| Contact | Site | Operator |
|---|---|---|
| N-SAR1-GW 00:31 | GW-01 | You - link proven, REC-PLAYBACK commanded |
| N-SAR1-SH 00:33 | SH-02 | Fiona (her last before she goes off) |
| N-SAR2-SH 02:54 | SH-02 | You, remote - telemetry contact |
| N-SAR2-GW 04:27 | GW-01 | You - steep pass, imagery |
| N-SAR2-SH-2 04:25 | SH-02 | Dropped (P3) |
Night Tasking
Section titled “Night Tasking”COMSEC
Section titled “COMSEC”| Item | State |
|---|---|
| Command-link key | Scheduled rotation pending; arrived on the night shift, as they do |
| Procedure | TT&C COMSEC panel: Initiate Key Rotation, then Confirm Key Rotation |
| Required before send | Key status Valid |
| Zeroize | Not part of a rotation |
| Fleet traffic key | Rolls on the fleet schedule at 04:15, as it does every Tuesday. The payload crypto reads Mismatch until the new material is loaded from the TX chain payload panel. The command key is a different key. |
Command Request MER-OPS-2027-0402
Section titled “Command Request MER-OPS-2027-0402”| Item | Value |
|---|---|
| Target | MERIDIAN-SAR-1 (NORAD 61701) |
| Command | REC-PLAYBACK |
| Window opens | 00:31:40 |
| Window closes | 00:38:30 |
| Requirements | Doppler compensation engaged; key Valid; acknowledged before LOS |
Acceptance Card GW-01-ATP-N01 (night pass geometry)
Section titled “Acceptance Card GW-01-ATP-N01 (night pass geometry)”| Parameter | Value |
|---|---|
| Satellite EIRP | 31.3 dBm |
| Slant range at max elevation | 581 km |
| Free-space path loss at 11,686 MHz | 169.1 dB (the afternoon card was 171.4 dB at 761 km; 20 log(761 / 581) = 2.3 dB) |
| GW-01 receive antenna gain | 50.4 dBi |
| System noise temperature | 121 K |
| Occupied bandwidth | 36 MHz |
| Implementation loss | 1 dB |
| Design figure, predicted C/N | ~13.8 dB (worksheet must agree within 1.0 dB) |
| Demodulator threshold | 4.2 dB C/N (QPSK 3/4: Es/N0 5.0 dB in the 30 Msps carrier) |
| Required margin at Accept Link | 5.0 dB (C/N 9.2 dB), measured live |
| Strong segment (C/N at or above 8 dB) | 00:33:10 to 00:37:00 |
Reference: C/N = EIRP + Grx − FSPL − Limpl − 10 log10(k · Tsys · B), k = −228.6 dBW/K/Hz. The survey quotes EIRP in dBm.
Chain order
Section titled “Chain order”The chain stays cold until the downlink is proven: an uplink on this rack spoils the receive measurement, and Accept Link samples the live C/N. Then, inside the window: uplink Doppler compensation on the TT&C console; transmit modem on air into the muted BUC; unmute; HPA enable. Down after LOS: HPA off, BUC muted, carrier off. Nobody checks the order for you tonight.
The Other Two Contacts
Section titled “The Other Two Contacts”02:54 from Shetland: telemetry, on holdover
Section titled “02:54 from Shetland: telemetry, on holdover”A 13° pass at 1,233 km will not meet the imagery delivery standard: expect C/N to peak near 6.6 dB, a clean lock with only a couple of dB over threshold and well short of the 8 dB delivery line. Hold lock above 5 dB through culmination for the state-of-health frames. That is 20 log(1233 / 581) = 6.5 dB more path loss than the 00:31 pass, plus atmosphere at 13°. A site is underperforming only when its number is worse than its geometry.
The SH-02 GNSS antenna has been unreliable in the wind. If the GPS Timing panel shows the receiver locked with HOLDOVER active, the GNSS input switch up and zero satellites, that is an outage at the site, not a switch left down. The disciplined oscillator coasts on its last correction; a few minutes of holdover is a few microseconds and a few hertz at Ku. Fly the pass on it, leave the switch alone (cycling it cannot conjure a signal), and confirm re-lock when the signal returns. Then put the outage in the handover: the day shift decides whether it was weather or a failing antenna, and cannot decide without the record.
04:27 over Galway: steep, after the key roll
Section titled “04:27 over Galway: steep, after the key roll”Peak C/N near 16.5 dB at 73° and 408 km, the best number of the night. The azimuth rate at the top of a 73° pass is a few degrees a second, inside what the 10°/s pedestal can do; the keyhole is a near-zenith problem, for a different shift. Before AOS, read the payload crypto: the fleet traffic key rolled at 04:15 and the station did not follow. Re-key from the TX chain payload panel (one load, both directions) and confirm TX and RX read Valid, or the imagery will not decrypt.
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 | IF (MHz) | RF (MHz) | Format |
|---|---|---|---|
| SAR-1 imagery downlink | 1,414 | 11,686 | QPSK 3/4, 36 MHz |
| SAR-1 telemetry beacon | 1,389 | 11,711 | CW |
| SAR-1 telecommand uplink | 1,405 | 14,005 | QPSK 3/4, 36 MHz, −7 dBm modem |
| SAR-2 imagery downlink | 1,370 | 11,730 | QPSK 3/4, 36 MHz; both sites retune to it |
Doppler: ±270 kHz on the downlink (receiver follows), ±325 kHz on the uplink (compensated at the TT&C console, required for an ACK). A 40° pass has a higher peak range rate than the afternoon passes; the compensation handles it, provided it is on.
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° | Program-track available; elements current |
| LNB | 13,100 MHz LO, reference locked | Stable |
| GPSDO | Locked, 9 satellites | Disciplined |
| RX modem 1 | 1,414 MHz / 36 MHz / QPSK 3/4 | SAR-1 imagery; retune to 1,370 MHz for the 04:27 pass |
| TX modem 1 | 1,405 MHz / 36 MHz / QPSK 3/4 / −7 dBm | Not transmitting |
| BUC | 12,600 MHz LO, reference locked | No drive present; stays that way until the link is proven |
| HPA | Powered, output disabled | Modem on air before this goes live; off before the carrier stops |
| Payload crypto | ACTIVE, traffic key Valid | Rolls at 04:15 |
| Link Analysis console | Night card loaded, worksheet blank | |
| Contact Plan console | Five contacts, none allocated | Reads UNALLOCATED |
SH-02 Shetland (as Fiona leaves it at 0100)
Section titled “SH-02 Shetland (as Fiona leaves it at 0100)”| Equipment | Status | Notes |
|---|---|---|
| 4 m Ku tracker | Powered, manual, parked az 5° / el 3° | Program-track available |
| GPSDO | Locked, 9 satellites | Watch it |
| RX modem 1 | 1,414 MHz | Her SAR-1 carrier. Retune to 1,370 MHz for SAR-2. |
| BUC / HPA | Muted / output disabled | No uplink tasking |
Qualification Checklist
Section titled “Qualification Checklist”Before AOS (00:15 – 00:31)
Section titled “Before AOS (00:15 – 00:31)”- Contact plan: required contacts allocated, no site double-booked, P3 overhead dropped, reads DECONFLICTED
- COMSEC: rotation initiated and confirmed, command key Valid
- Link Analysis: worksheet computed, prediction agrees with the card
- GPS Timing: GPSDO locked; TX Chain: BUC on external reference; chain cold
Contact 1 (00:31 – 00:39)
Section titled “Contact 1 (00:31 – 00:39)”- Program-track on MERIDIAN-SAR-1; beacon on RX analysis
- RX modem locked on 1,414 MHz; Accept Link pressed in the strong segment with live margin ≥ 5 dB
- TT&C: uplink Doppler compensation engaged; modem on air; BUC unmuted; HPA enabled
- REC-PLAYBACK sent; ACK before 00:38:30
- After LOS: HPA off, BUC muted, carrier off; contact logged
Contact 2, Shetland remote (02:52 – 03:01)
Section titled “Contact 2, Shetland remote (02:52 – 03:01)”- SH-02 selected: BUC temperature normal, LNB stable, RX modem 1 to 1,370 MHz
- GPS Timing read: holdover diagnosed, switch left alone
- Program-track on MERIDIAN-SAR-2; carrier on Shetland’s RX analysis; lock, C/N ≥ 5 dB through culmination
- After 02:59: GNSS receiving again, holdover cleared; contact and outage logged
Contact 3, Galway (04:23 – 04:35)
Section titled “Contact 3, Galway (04:23 – 04:35)”- GW-01 selected: payload crypto reads Mismatch; re-keyed; TX and RX Valid
- RX modem 1 to 1,370 MHz; program-track on MERIDIAN-SAR-2; carrier on RX analysis
- Lock, C/N ≥ 8 dB through the top; payload decrypting
Handover
Section titled “Handover”- Plan, both keys, the outage record, the state of both sites
End of Briefing
Section titled “End of Briefing”Two sites, two birds, one operator, and no one on the other end of the phone who is expecting it to ring. The plan you build tonight is the one Fiona flies. The key you rotate is the one the day shift commands on. The card you sign is the one Rotterdam schedules against. The outage you write down is the one the day shift decides about.
Everything on this shift you have already done once. Do it again, in order, without being told.
Good luck.