Scenario 3 - Weather Emergency Handover

Shift Turnover Notes

Date: Tuesday, 1045 Local Station: Vermont (VT-01) Operator on Duty: You Supervisor: Charlie Brooks (present) Maine Station: ME-02 (unmanned, Catherine Vega en route)

Weather service just upgraded the forecast to a blizzard warning. Snow started falling about ten minutes ago and it’s coming down hard. Link margin to TIDEMARK-1 is already degrading - we’ve got maybe fifteen minutes before the carrier drops under its lock threshold.

Maine is 150 miles northeast with clear skies. Catherine is driving in now - should arrive in about ten minutes. We need to get the backup site configured and execute the handover before Vermont goes dark.

This is your first multi-site handover. I’ll walk you through it, but you’re doing the work.

— Charlie

Catherine (text message, 1038):

On my way in. Roads are still clear up here. ETA 10-15 min depending on how the plow situation looks. Don’t wait for me - get Maine configured remotely and I’ll verify on-site when I arrive.

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Active Services

Satellite	Customer	Service Type	Status
TIDEMARK-1	Teleport Services Inc.	Enterprise Data	Operational (degrading)

TIDEMARK-1 provides backbone connectivity for several enterprise customers in the northeastern corridor. Service interruptions impact multiple downstream clients - banks, hospitals, regional carriers. Every minute of downtime is visible.

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TIDEMARK-1 Link Parameters

Frequency Allocation

Parameter	RF (MHz)	LO (MHz)	IF (MHz)
Beacon (Downlink)	4,175.5	5,250 (LNB)	1,074.5
Carrier (Downlink, TP-1)	3,718	5,250 (LNB)	1,532
Carrier (Uplink, TP-1)	5,943	7,000 (BUC)	1,057

Both LOs sit above their RF: IF = LO - RF on the downlink, RF = LO - IF on the uplink (the BUC panel shows lower sideband, LSB).

Modem Configuration

Direction	Frequency (IF)	Bandwidth	Modulation	FEC	Power
Receive	1,532 MHz	36 MHz	QPSK	3/4	—
Transmit	1,057 MHz	36 MHz	QPSK	3/4	-7 dBm

LNB Configuration

Parameter	Value
LO Frequency	5,250 MHz
Gain	65 dB (Vermont’s setting; the LNB powers up at 65 dB)
Reference	External (GPSDO 10 MHz)

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Weather Briefing

Current Conditions (1045):

• Temperature: 26°F (-3°C)
• Wind: NW at 25 mph, gusts to 40
• Precipitation: Heavy snow, 2+ inches/hour
• Visibility: 0.25 miles

Forecast (next 6 hours):

• Blizzard conditions continuing through 1700
• Additional accumulation: 12-18 inches
• Wind-driven snow creating significant signal attenuation

Link Impact:

• Clear-sky C/N on the TIDEMARK-1 carrier: about 12.7 dB. For QPSK 3/4 the modem shows Required Es/N0 5.0 dB; with Es/N0 about 0.8 dB above Raw C/N it acquires lock from about 4.7 dB C/N (Required 5.0 plus a 0.5 dB acquisition margin, less the 0.8 dB Es/N0 offset) and holds it down to about 3.7 dB, so Vermont starts with roughly 8 dB of margin over the acquisition point.
• At C-band, falling snow itself costs well under 1 dB. The damage comes from snow and ice loading the feed: the first dB of ice on the feed takes about 3 dB off C/N, because the wet feed both absorbs the carrier and radiates its own noise into the LNB. About 4 dB of ice is enough to lose lock.
• The feed heater is sized for about an inch of snow an hour in moderate wind. At 2+ inches an hour with 40 mph gusts stripping its heat, the snow loads the feed faster than the heater melts it: with the heater on, ice still builds, only slower. Projected at storm peak: Vermont cannot hold lock (the modem holds QPSK 3/4 down to about 3.7 dB C/N), roughly fifteen minutes out. The heater buys time and protects the feed; plan to be off VT-01 before then.
• Timing is unaffected: snow in the air costs under 1 dB at L-band too, and the GPSDO’s GPS antenna is a sealed patch under a radome with no feed to load, so both GPSDOs stay GNSS-locked.

Caution

Don’t wait for the AGC to warn you. The AGC card shows its Gain (dB), its Input level (dBm) and its Output level (dBm). VT-01’s AGC holds the output at -30 dBm and has a 10 dB maximum gain. It levels the total power it sees, carrier plus noise, so as the feed loads up the input level drops only a dB or two and the gain rises by the same amount. At VT-01 the gain reads about -2.5 dB in clear sky and is still under +1 dB when the carrier loses lock; the card never gets near At Max. Watch the carrier’s C/N on RX Analysis: that is the number that tells you how much time you have.

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Station Reference

Vermont (VT-01) - Primary

Equipment	Current State	Notes
GPSDO	Locked	Timing reference stable
LNB	Powered, locked	Weather degrading signal
BUC	Powered, unmuted	Currently transmitting
HPA	Enabled	Active uplink
Antenna	Program-track on TIDEMARK-1
Feed Heater	Needs activation	Enable: slows the ice, cannot stop it at storm peak

Maine (ME-02) - Backup

Equipment	Current State	Notes
GPSDO	Locked	Verify before configuring RF
LNB	Powered off	Cold start required (the alarm bar shows “LNB powered off - no receive path” until it is on)
BUC	Muted	Will enable during handover
HPA	Disabled	Will enable during handover
TX Modem	Powered off, parked from its last job	Power on and set to match Vermont
RX Modem	Parked from its last job	Set to match Vermont
Antenna	Stowed (El: 90°)	Point to TIDEMARK-1
Feed Heater	Standby	Clear weather, not needed

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Weather Handover Procedure (SOP-WX-003)

Operations rolled out this procedure last month after the January ice storm revealed gaps in our ad-hoc approach. This is the first time VT-01 has needed to execute it.

Caution

Maine’s look angles differ from Vermont’s. Program Track calculates correct pointing automatically - never manually enter Vermont’s coordinates at Maine. The TIDEMARK-1 satellite page lists both: “Az / El from VT-01” and “Az / El from ME-02”, about 4° apart in azimuth.

Pre-Handover: Protect Vermont

• Enable feed heater on Vermont ACU
• Note the AGC Gain (dB) and Input (dBm), and the carrier’s C/N

Backup Site Activation (Maine)

Timing Verification

• GPSDO locked
• GNSS signal present

Antenna

• Tracking mode: Program Track (PROGRAM)
• Target: TIDEMARK-1, then press Move to Target
• Position reached

Receive Chain

• LNB powered, LO: 5,250 MHz, Gain: 65 dB
• LNB ready: LOCK shows LOCKED, noise temperature under 100 K, Thermal reads Stable (a cold LNB warms up for about 90 s after power-on)
• Spectrum analyzer: Center 1,074.5 MHz, Span 0.002 MHz (2 kHz; the span field is in MHz), Min Amp -100 dBm, Max Amp -30 dBm, RBW Auto (3 Hz at this span; at 1 MHz RBW the CW beacon is buried in the noise). The beacon reads around -60 to -55 dBm
• Beacon visible at 1,074.5 MHz IF

Receiver (Modem)

• Frequency: 1,532 MHz
• Bandwidth: 36 MHz, Mod: QPSK, FEC: 3/4
• Carrier lock confirmed
• C/N ≥ 10 dB

Transmitter (Modem)

• Modem powered on
• Frequency: 1,057 MHz, Power: -7 dBm
• Bandwidth: 36 MHz, Mod: QPSK, FEC: 3/4
• Transmission enabled

Traffic Transfer

• Select TIDEMARK-1 in the asset tree to open its satellite page
• Execute transfer: VT-01 → ME-02 (break-before-make: Vermont’s HPA and BUC drop and Maine’s come up in the same step; two sites radiating one carrier would interfere)
• Verify service continuity (zero packet loss target)

Post-Handover: Stow Vermont

• Return to Vermont station view
• Set tracking mode: Stow (click STOW, then APPLY on the Antenna Positioning card)
• Confirm antenna reaches stow position (El: 90°)
• Leave the feed heater on: stow takes the reflector’s face out of the wind, but a face-up dish still collects snow

Handover Log Entry

Type the handover into the Ops Log (station sidebar) before you sign off. Every weather handover gets an entry, even a clean one:

• Time the weather started degrading the link, and time the handover completed
• Satellite and services affected (TIDEMARK-1, enterprise data)
• Stations involved (VT-01 to ME-02)
• Weather conditions at the primary site
• Anything abnormal you saw during the transfer

The log is what post-incident review and seasonal pattern analysis run on.

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AGC Reference

What the VT-01 AGC card shows (output target -30 dBm, maximum gain +10 dB):

Readout	Clear sky	Feed loaded, near loss of lock	What it tells you
Gain	about -2.5 dB	about +0.5 dB	How hard the AGC is working. A few dB of movement is normal.
Input	about -27.5 dBm	about -30.5 dBm	Total power arriving at the AGC: carrier plus noise
Output	-30.0 dBm	-30.0 dBm	Held at target; a steady output says nothing about link health
Mode	Active	Active	At Max means the gain has reached +10 dB: there is almost no carrier left to level (pre-acquisition, a dead LNB)

The AGC keeps the level steady for the modem. It cannot restore C/N: it turns the noise up and down with the carrier. Judge the link by C/N and lock margin, not by the AGC.

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Escalation Guidelines

Handle Yourself:

• Weather handover execution (you’re trained for this)
• Feed heater activation
• Equipment configuration at backup site
• Traffic transfer between stations

Inform Charlie:

• Handover complete (so he can update NOC)
• Any equipment faults during handover
• Service impact beyond expected transition

This is routine for winter operations. Work methodically and you’ll be fine.

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End of Briefing

The clock is running. Snow is degrading Vermont’s link and the AGC is working harder every minute. Catherine will arrive at Maine shortly, but you need to get the station configured before she walks in the door.

Charlie is watching, but he expects you to execute. This is what multi-site operations look like in the Northeast - routine procedure, but time-critical.

Get Vermont’s feed heater on, bring Maine online, execute the handover, and stow Vermont’s antenna before the storm gets worse.

Clock’s ticking.