Scenario 23 - Dark Passes

Shift Turnover Notes

Date: Saturday 24 April, 2100 UTC Station: GW-01 Galway, Ireland - NATS Europe (the only station on the network with the command key) Operator on Duty: You, qualified, solo Constellation Ops: Anneke Visser, Rotterdam (keys the spacecraft end of the hop set on your call) Site Lead: Charlie Brooks (on the phone) Group Security: Priya Sharma, NATS Group CSIRT (IAR-2027-0422-GW01 issued Thursday)

SAR-2 payload thermal excursion +6 °C over limit since 20:58; Rotterdam requests PLD-SAFE on the 21:22 GW-01 window. KEY-2027-Q2b live. HOP-SAR2-05 staged at both ends, inactive. TX modem on 1,405; RX on 1,414; BUC muted. Element sets current. Nothing on the board.

• Day shift (turnover log, 2050)

Priya (text, 2040):

“The report went out Thursday with their method in it, and I would bet they have read it. Anneke needs PLD-SAFE on the 21:22 pass - the payload is warming. If they come tonight they will come with everything at once, because one at a time did not work. Nothing they have done needs a new answer. It needs the answers in the right order.”

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Today’s Passes (epoch 21:00:00 UTC, 0° horizon, Galway)

Satellite	AOS	Rise az	Max el	Culmination	LOS	Set az	Work
MERIDIAN-SAR-2	21:22:01	022°	32.8°	21:26:50 (663 km)	21:31:35	177°	Commanding, window 21:22:21-21:31:15; PLD-SAFE
MERIDIAN-SAR-1	21:39:58	004°	27.0°	21:44:44 (788 km)	21:49:27	221°	Not tasked

The SAR-2 times are for the post-burn orbit. The set on the station at 21:00 is the pre-burn one.

Frequency Plan (MER-IF-2027-04b)

Signal	RF	IF	LO
SAR-2 TT&C uplink	14,035 MHz	1,435 MHz (TX)	BUC 12,600 low-side: IF = RF − LO
SAR-2 video	11,730 MHz	1,370 MHz (RX)	LNB 13,100 high-side: IF = LO − RF
SAR-2 beacon	11,703 MHz	1,397 MHz
Hop set HOP-SAR2-05	14,031 / 14,033 / 14,035 / 14,037 / 14,039 MHz		five channels around the fixed carrier

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The Surge

At 21:14, inside a minute:

What	Where you see it	What it costs
GNSS spoof	GPS Timing: ΔT walking, constellation healthy	Timestamps, and 2 ppm on every LO (tens of kHz, inside the Doppler). Nothing on the pass
SAR-2 debris-avoidance burn	Pass Schedule: EPHEMERIS STALE against SAR-2	The pass. Program-track points where the bird was
Jammer expected in the window	Nowhere yet - the carrier is clear	Nothing, until it is on the air

Three things, eight minutes, one command. None of them is a fault on the station. Each has a ten-second answer. The whole exam is the order.

Caution

Rank by what loses the pass, not by what alarmed first. A stale element set loses it outright: at 660 km, a few seconds along-track is a beamwidth, and program-track does not search. A walking reference costs two microseconds a second in timestamps and can wait four minutes. A jammer that is not on the air costs nothing until it is - and a hop set spent on a forecast is a hop set gone.

The Order

Step	Where	Time it takes
1. Load Updated Ephemeris (SAR2-DAM)	Pass Schedule inbox	One click; the slew is immediate
2. GNSS switch down	GPS Timing, Lock & Power card	Ten seconds; holdover ACTIVE, ΔT frozen
3. Nothing	Security console	The key stays in the store until a denial is called

Then the pass as normal: pre-position on 022°, program-track on the post-burn set, chain up at 21:22:21, HK-DUMP on the fixed carrier. The ACK proves the holdover: a free-running OCXO is a perfectly good 10 MHz for Doppler compensation, the modem clock and the BUC LO. Only the timestamps carry the offset.

The Denial

From 21:24:30 PLD-SAFE comes back Uplink denied - carrier jammed. Key Valid, Doppler engaged, window OPEN, reference in holdover.

Suspect	Why it is not
The holdover reference	HK-DUMP ACKed on it four minutes earlier; an OCXO drifts nanoseconds an hour. Putting GNSS back hands the reference to the spoofer again
The key	Valid at both ends; a key rejection is its own reason on the console
Standing down	Shetland has no command key; the payload has no next window

The answer is the one it was on the 16th, with everything else still broken around it: call it, Anneke keys SAR-2, Load Hop-Set Key, Frequency hopping, SYNC LOCKED, resend. PLD-SAFE goes up on a set they did not control, a reference they could not reach and a sequence they did not have.

Note

Two hop sets spent on the same carrier in eight days is a pattern. The response is still a called hop - but HOP-SAR2-06 is staged closer, the switch is expected on the first NAK, and it is written into the pre-pass sweep. Hopping from AOS burns a set on every pass that is not denied.

Surge Log SL-2027-0424-GW01

Section	Line
Surge	What arrived at 21:14, the order it was dealt with, the post-burn set loaded
Window	HK-DUMP, the NAK and its reason, the call, the hop, PLD-SAFE ACK
Debrief	Simultaneous faults ranked by what loses the pass; what is staged for next time

The reference stays in holdover until a probe says the sky is honest. There is a storm forecast for Tuesday.