Scenario 6 - Old Faithful

Duration: 25-30 minutes Difficulty: Beginner Mission Type: Satellite Link Establishment

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Shift Turnover Notes

Date: Thursday, 1400 Local Station: Vermont (VT-01) Operator on Duty: You Supervisor: Charlie Brooks (present)

Maine has been carrying AURORA-7 traffic for the past month while we finished the antenna upgrades. Now that VT-01 is back online, we’re taking the service back.

AURORA-7 is a legacy bird - stopped north-south station-keeping years ago to conserve fuel. The orbit’s inclined now. Maine had some signal dropouts when they first took over because they tried running program-track. Don’t make the same mistake.

I’ve already configured the beacon receiver and verified the encryption keys. You handle the rest - antenna, RF chain, modems. Show me you understand why this satellite needs different handling.

— Charlie

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Active Services

Satellite	Customer	Service Type	Status
AURORA-7	Pacific Rim Communications	Maritime VSAT	Transferring from ME-02

Pacific Rim Communications provides connectivity for fishing fleets in the North Pacific. Their vessels rely on AURORA-7 for weather data, catch reporting, and crew welfare communications. Maine has been covering the service - now it’s Vermont’s responsibility.

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AURORA-7 Operations Reference

AURORA-7 is a legacy C-band satellite that’s been in service for over 15 years. To conserve fuel, the operators stopped north-south station-keeping years ago, which means its orbit is now inclined. From our perspective, it traces a figure-8 pattern in the sky over each 24-hour period.

Caution

AURORA-7 requires step-track mode. Program-track cannot compensate for orbital inclination drift. Maine learned this the hard way - intermittent dropouts until they switched tracking modes.

Orbital Characteristics

Parameter	Value	Notes
Orbital Inclination	~5°	Accumulated since station-keeping stopped
Daily Motion	Figure-8 pattern	North-south excursion over 24 hours
Program-Track Accuracy	Insufficient	TLE assumes geostationary position

Tracking Mode Selection

Satellite Type	Recommended Mode	Reason
Geostationary (active S/K)	Program-track	Satellite stays at fixed position
Inclined orbit	Step-track	Follows actual satellite position via beacon

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AURORA-7 Link Parameters

Frequency Allocation

Parameter	RF (MHz)	LO (MHz)	IF (MHz)
Beacon (Downlink)	4,165	5,250 (LNB)	1,085
Carrier (Downlink)	3,605	5,250 (LNB)	1,645
Carrier (Uplink)	5,830	4,925 (BUC)	905

IF Calculation Reference

Downlink (High-side LO):

IF = LO - RF

Uplink (Low-side LO):

IF = RF - LO

Note

The BUC uses low-side injection for upconversion. TX IF calculation is different from RX: IF = RF - LO, not LO - RF.

Modem Configuration

Direction	IF (MHz)	Bandwidth	Modulation	FEC
Receive	1,645	24 MHz	QPSK	3/4
Transmit	905	24 MHz	QPSK	3/4

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Station Reference

Vermont (VT-01) - Current State

Equipment	Status	Notes
GPSDO	Locked	Timing reference stable
Antenna	Program-track on TIDEMARK-1	Change target and mode
LNB	5,250 MHz LO, powered	No change needed
BUC	4,925 MHz LO, muted	Unmute after TX config
HPA	Disabled	Enable for transmission
Beacon Receiver	1,085 MHz IF	Pre-configured by Charlie
RX Modem	1,200 MHz (incorrect)	Configure to 1,645 MHz
TX Modem	1,050 MHz (incorrect)	Configure to 905 MHz
Encryption	AES-256-GCM	Keys verified by Charlie

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Security Configuration

Charlie has verified the encryption configuration for AURORA-7:

Parameter	Value
Algorithm	AES-256-GCM
Key Status	Valid
Mode	Authenticated encryption

Caution

Never transmit without verifying encryption status. Pacific Rim traffic includes vessel position data and crew communications - both require protection.

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Link Establishment Checklist

Antenna Acquisition

• Current target: Verify antenna is on TIDEMARK-1
• Change target: Select AURORA-7
• Tracking mode: Program-track (for initial acquisition)
• Antenna position: Wait for slew to complete
• Beacon signal: Visible on spectrum analyzer at 1,085 MHz IF

Step-Track Transition

• Tracking mode: Switch to step-track
• Beacon lock: Acquired (ACU shows “Tracking”)
• Signal quality: Stable (step-track optimizing)

Receive Chain

• Spectrum analyzer: Reconfigure for 1,645 MHz IF, 24 MHz span
• RX modem frequency: 1,645 MHz
• RX modem bandwidth: 24 MHz
• RX modem modulation: QPSK, FEC 3/4
• Carrier lock: Confirmed
• C/N ratio: ≥ 10 dB

Transmit Chain

• TX modem frequency: 905 MHz (calculated from RF - LO)
• TX modem bandwidth: 24 MHz
• TX modem modulation: QPSK, FEC 3/4
• Encryption: Verified active
• BUC: Unmuted
• HPA: Enabled

Full Duplex Verification

• RX modem: Locked with margin
• TX path: Active, no alarms
• Dashboard: All indicators green

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Quick Reference

Why Step-Track?

Program-Track	Step-Track
Uses TLE orbital predictions	Uses beacon signal strength
Assumes satellite at fixed position	Follows actual satellite position
No signal feedback	Continuously optimizes pointing
Works for geostationary satellites	Required for inclined orbits

Acquisition Sequence

1. Program-track points antenna to approximate position
2. Beacon becomes visible on spectrum analyzer
3. Switch to step-track mode
4. ACU optimizes pointing using beacon signal
5. Configure receive and transmit chains

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End of Briefing

Maine is standing by to hand over AURORA-7 traffic once you’ve established the link. Pacific Rim’s fishing fleet doesn’t know or care about our internal station transfers - they just need connectivity.

Charlie configured the beacon and encryption. The rest is on you: acquire the satellite, enable step-track, configure the modems, and bring up the full duplex link.

This is your first inclined-orbit satellite. Understand why step-track matters - you’ll work with more aging birds as they reach end-of-life and stop station-keeping.

Get the link up, and Maine can release the service to Vermont.