Scenario 2 - Scheduled Maintenance
Duration: 20-30 minutes
Difficulty: Beginner
Mission Type: Supervised Operations
Shift Turnover Notes
Date: Tuesday, 0930 Local
Station: Vermont (VT-01)
Operator on Duty: You
Supervising: Charlie Brooks (Senior Operator)
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
| 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
Work Order #: VT-2026-0142
Requested By: Facilities
Scheduled: 1000-1030 Local
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)
- Two-way radio confirmation before crew ascent
RF Safety Acknowledgment
Hazard Summary
The transmit chain at VT-01 includes a High Power Amplifier (HPA) capable of several hundred watts at C-band frequencies (5.85-6.725 GHz). 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
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
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. Verbal confirmation via radio is required before any transmit chain changes.
TIDEMARK-1 Operations Reference
Frequency Allocation
| Parameter | RF (MHz) | LO (MHz) | IF (MHz) |
|---|---|---|---|
| Beacon (Downlink) | 4,175.5 | 5,250 (LNB) | 1,074.5 |
Antenna Position
| Parameter | Operational | Maintenance |
|---|---|---|
| Azimuth | 161.8° | 0° |
| Elevation | 34.2° | 5° |
| Tracking Mode | Program-track | Manual |
The maintenance position (elevation 5°) tilts the dish low enough for crew access to the feed assembly while clearing horizon obstructions.
LNB Parameters
| Parameter | Value |
|---|---|
| LO Frequency | 5,250 MHz |
| Gain | 60 dB |
| Thermal Stabilization | ~60 seconds after power-up |
Equipment Status at Shift Start
| Equipment | Current State | Notes |
|---|---|---|
| Antenna | Program-track on TIDEMARK-1 | Operational position |
| LNB | Powered, reference locked | Receiving beacon |
| BUC | Powered, muted | Standard standby |
| HPA | Powered, output disabled | Ready state |
Power Sequencing Reference
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 | Mute BUC | Secure upconverter |
| 4 | Power down LNB | Shutdown receive path |
| 5 | Command antenna to maintenance position | Safe access for crew |
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 | Wait for LNB thermal stabilization | Indicator turns green |
| 4 | Verify beacon on spectrum analyzer | Confirm pointing correct |
| 5 | Unmute BUC | Enable TX path |
| 6 | Power on HPA | Energize amplifier |
| 7 | Enable HPA output | Restore full service |
Pre-Maintenance Checklist
Before Calling “RF Secured”
- HPA output: Disabled
- HPA power: Off
- BUC: Muted
- LNB: Powered off
- Antenna: At maintenance position (Az 0°, El 5°)
- Radio confirmation: Received from maintenance lead
Post-Maintenance Verification Checklist
Receive Path
- LNB reference: Locked (indicator green)
- Antenna position: 161.8° Az, 34.2° El
- Tracking mode: Program-track
- Beacon: Visible at 1,074.5 MHz IF
- Signal strength: Nominal
Transmit Path
- BUC: Unmuted
- HPA: Powered on
- HPA output: Enabled
- No alarms on dashboard
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, confirm with Mike on the radio, then hold position until he calls the work complete. 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.