Scenario 2 - Scheduled Maintenance
Duration: 25-35 minutes
Difficulty: Beginner
Mission Type: Supervised Operations
Shift Turnover Notes
Section titled “Shift Turnover Notes”Date: Tuesday, 0930 Local
Station: Vermont (VT-01)
Operator on Duty: You
Supervising: Charlie Brooks (Senior Operator)
Morning Briefing from Charlie
Section titled “Morning Briefing from Charlie”Charlie pulled you aside after the morning standup:
“Good timing on your second day - we’ve got a maintenance window this morning. Nothing complicated, just a waveguide gasket replacement on the TIDEMARK-1 feed. But it’s a good chance for you to run through a full power-down and recovery sequence.
I’ll be right here if you need me, but I want you at the controls. The maintenance crew is already on site - they’re waiting on us to secure the RF before they climb up.
Take your time. Get it right. Speed comes later.”
Active Services
Section titled “Active Services”| Satellite | Customer | Service Type | Status |
|---|---|---|---|
| TIDEMARK-1 | SeaLink Maritime | C-band VSAT | Operational |
SeaLink has been notified of the maintenance window. They’ve scheduled non-critical traffic around our downtime, so there’s no pressure - but they do expect us back online within 30 minutes.
Maintenance Work Order
Section titled “Maintenance Work Order”Work Order #: VT-2026-0142
Requested By: Facilities
Scheduled: 0930-0950 Local (crew on the feed as soon as the RF is secured, about 0935; Mike calls the work complete at 0950)
Work Description:
Replace waveguide flange gasket on TIDEMARK-1 antenna feed assembly. Gasket showing signs of wear during quarterly inspection. Preventive replacement to avoid moisture ingress.
Crew: Mike Chen (Lead), rotating apprentice
Requirements:
- RF transmit chain secured before crew approaches feed
- Antenna positioned for feed access (maintenance position)
- Crew-clear confirmation before any transmit chain changes (Charlie relays Mike’s radio calls)
RF Safety Acknowledgment
Section titled “RF Safety Acknowledgment”Hazard Summary
Section titled “Hazard Summary”The transmit chain at VT-01 includes a High Power Amplifier (HPA) rated at 1 kW (60 dBm at its 1 dB compression point) at C-band frequencies (5.85-6.725 GHz). At the standard 10 dB back-off it delivers about 100 W to the feed. At these levels:
- Thermal burns from direct feed exposure
- RF radiation hazard to eyes and tissue
- Induced currents in metal objects near the feed
Exclusion Zone
Section titled “Exclusion Zone”No personnel within 3 meters of the feed horn while the transmit chain is energized. This applies even with the HPA disabled but BUC unmuted - residual RF can still cause injury at close range.
Your Responsibility
Section titled “Your Responsibility”As the operator on console, you control access to the exclusion zone. Never re-enable transmit equipment while maintenance personnel are on the antenna structure. Mike confirms crew-clear by radio before any transmit chain changes; Charlie relays his calls to you on console, and you acknowledge them on the checklist.
TIDEMARK-1 Operations Reference
Section titled “TIDEMARK-1 Operations Reference”Frequency Allocation
Section titled “Frequency Allocation”| Parameter | RF (MHz) | LO (MHz) | IF (MHz) |
|---|---|---|---|
| Beacon (Downlink) | 4,175.5 | 5,250 (LNB) | 1,074.5 |
Antenna Position
Section titled “Antenna Position”| Parameter | Operational | Maintenance |
|---|---|---|
| Azimuth | 153.2° | Unchanged |
| Elevation | 35.2° | 5° |
| Tracking Mode | Program-track | Maintenance (MAINT) |
The maintenance position (elevation 5°) tilts the dish low enough for crew access to the feed assembly while clearing horizon obstructions. Only elevation moves; azimuth stays where it was.
On the ACU Control tab, clicking a mode button only stages the move (the card shows “MAINTENANCE pending APPLY” and the Mode still reads the old mode): press APPLY on the Antenna Positioning card to start it. To return to the satellite, click PROGRAM, select TIDEMARK-1 as the target and press Move to Target.
LNB Parameters
Section titled “LNB Parameters”| Parameter | Value |
|---|---|
| LO Frequency | 5,250 MHz |
| Gain | 60 dB (the panel reads 65 dB after a power cycle; set it back to 60) |
| Ready indicators | LOCK shows LOCKED, noise temperature back near 43 K (about 90 seconds of warm-up after power-on) |
Equipment Status at Shift Start
Section titled “Equipment Status at Shift Start”| Equipment | Current State | Notes |
|---|---|---|
| Antenna | Program-track on TIDEMARK-1 | Operational position |
| LNB | Powered, reference locked | Receiving beacon |
| TX Modem | Transmitting | Customer traffic |
| BUC | Powered, unmuted, transmitting | Live link |
| HPA | Powered, enabled, 10 dB backoff | Transmitting to TIDEMARK-1 |
Power Sequencing Reference
Section titled “Power Sequencing Reference”Shutdown Sequence (Transmit → Receive → Antenna)
Section titled “Shutdown Sequence (Transmit → Receive → Antenna)”Disable highest-power components first to eliminate hazard quickly:
| Step | Action | Why |
|---|---|---|
| 1 | Disable HPA output | Stop RF radiation |
| 2 | Power off HPA | Fully de-energize amplifier |
| 3 | Power off BUC | Fully de-energize upconverter |
| 4 | Stop TX modem transmitting | No IF drive into a dead chain |
| 5 | Power down LNB | Shutdown receive path |
| 6 | Command antenna to maintenance position | Safe access for crew |
Startup Sequence (Antenna → Receive → Transmit)
Section titled “Startup Sequence (Antenna → Receive → Transmit)”Point and verify before enabling transmit:
| Step | Action | Why |
|---|---|---|
| 1 | Command antenna to operational position | Establish signal path |
| 2 | Power on LNB (5,250 MHz LO, 60 dB gain) | Enable receive chain |
| 3 | Confirm LNB LOCK and noise temperature | Receive path ready |
| 4 | Retune the spectrum analyzer to the beacon and verify it | Confirm pointing correct |
| 5 | Start TX modem transmitting | IF drive present |
| 6 | Power on BUC | Enable TX path |
| 7 | Power on HPA | Energize amplifier |
| 8 | Enable HPA output | Restore full service |
Pre-Maintenance Checklist
Section titled “Pre-Maintenance Checklist”Before Calling “RF Secured”
Section titled “Before Calling “RF Secured””- HPA output: Disabled
- HPA power: Off
- BUC: Powered off
- TX modem: Not transmitting
- LNB: Powered off
- Antenna: At maintenance position (El 5°)
- Crew cleared to climb (Charlie relays the all-clear once the dish is at 5°)
Post-Maintenance Verification Checklist
Section titled “Post-Maintenance Verification Checklist”Before Restoring Anything
Section titled “Before Restoring Anything”- Crew clear of the antenna confirmed at 0950 (quiz), before the dish moves or any RF equipment comes back on
Receive Path
Section titled “Receive Path”- LNB reference: Locked (indicator green)
- Antenna position: 153.2° Az, 35.2° El
- Tracking mode: Program-track
- Spectrum analyzer: Retuned to Center 1,074.5 MHz, Span 0.002 MHz (2 kHz)
- Beacon: Visible at 1,074.5 MHz IF
- Signal strength: Nominal
Transmit Path
Section titled “Transmit Path”- TX modem: Transmitting
- BUC: Powered on, unmuted
- HPA: Powered on
- HPA output: Enabled
- No warning or critical alarms on dashboard
End of Briefing
Section titled “End of Briefing”The maintenance crew is standing by. Mike’s done this replacement dozens of times - he just needs you to secure the RF so his team can work safely.
Run through the shutdown sequence, wait for Charlie to relay Mike’s crew-clear call, then hold position until he calls the work complete. The gasket job runs to 0950 on the station clock: keep the dish parked at 5° and wait it out, or use the skip control in the command bar (“Skip to 09:50”) once the antenna is at the maintenance position. Take your time on the recovery - SeaLink would rather wait an extra five minutes than have you rush and miss a step.
Charlie’s watching, but this is your show.
You’ve got this.