Scenario 19 - Frequency Agility

Shift Turnover Notes

Date: Friday 16 April, 1300 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) Group Security: Priya Sharma, NATS Group CSIRT (INC-2027-0412-GW01 open)

IF plan MER-IF-2027-04b applied 21:10 last night. Hop set HOP-SAR2-04 loaded to the COMSEC store at 08:20, inactive. TX modem on 1,405 from yesterday’s SAR-1 tasking; RX on 1,414. BUC muted. Nothing on the board.

• Morning shift (turnover log, 1250)

Anneke (text, 1244):

“New IF plan is on your station as of last night. I loaded hop set HOP-SAR2-04 on SAR-2 at 08:20; your copy is in the store, inactive. SAR-2 at 13:20 is commanding: HK-DUMP, then PLD-STATUS. If your carrier is denied you call it and I key my end on the call - not before, the set is not free. SAR-1 after is receive only.”

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Today’s Passes (epoch 13:00:00 UTC, 0° horizon, Galway)

Satellite	AOS	Rise az	Max el	Culmination	LOS	Set az	Work
MERIDIAN-SAR-2	13:20:01	138°	27.9°	13:24:43 (765 km)	13:29:29	353°	Commanding, window 13:20:21-13:29:09
MERIDIAN-SAR-1	13:42:01	005°	25.2°	13:46:46 (839 km)	13:51:29	224°	Receive only

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
SAR-1 video	11,686 MHz	1,414 MHz
Hop set HOP-SAR2-04	14,031 / 14,033 / 14,035 / 14,037 / 14,039 MHz		five channels around the fixed carrier

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The Window

Two commands inside 13:20:21-13:29:09, in order: HK-DUMP, then PLD-STATUS. Chain up before the first (carrier into the muted BUC, unmute, HPA), chain down at LOS in the mirror order.

The console gives four reasons for a NAK. Three of them are its own:

NAK reason	What to check	Fix
Uplink not compensated	TT&C console Doppler toggle	Engage it
COMSEC key invalid	TX chain key badge	Rotate
Outside command window	Window badge	Wait
Uplink denied - carrier jammed	Everything above reads clean; the transponded return on the analyzer shows a carrier that is not yours	Hop

Caution

A NAK with the key reading Valid at both ends, Doppler engaged and the window OPEN is not a station problem and not a key problem. It is the satellite failing to hear you because something louder is sitting on your uplink frequency at the bird. Rotating a good key in an open window spends the window on nothing. Standing down hands them the window.

The Hop Set

Frequency hopping is only agile to someone who does not have the sequence. The key is the sequence. Both ends must load it - Anneke on SAR-2, you on the Security console - or one of you is transmitting into nothing.

Step	Where	What you see
Call the denial	The decision	Anneke keys SAR-2 on your call
Load Hop-Set Key	Security console, TRANSEC card	Key badge LOADED
Waveform mode → Frequency hopping	Same card	Sync badge SYNC LOCKED
Resend PLD-STATUS	TT&C console	ACK received - through the jamming

What hopping changes: your carrier is spread over five channels a jammer parked on one cannot cover, and the bird follows because it has the sequence. What it does not change: the jammer is still there, the set is now spent, and the report still has to say what was seen.

Note

A hop set used on the air is a hop set observed. HOP-SAR2-04 is retired tonight and the next set is staged before the next commanding pass. You hop on a called denial - not from AOS. Hopping every pass burns a set for a denial that may not come.

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SAR-1 Afterwards

Receive only, nothing of yours on the air. Uplink denial is aimed at the satellite; downlink interference is aimed at the station. A jammer that was on 14,035 MHz at SAR-2 has no reach into what SAR-1 sends you on 11,686. Decode it clean and write down that it was clean; that line is part of the picture too.

Uplink Denial Record UD-2027-0416-GW01

Section	Line
Window	The clean ACK, the NAK and its reason, what the console read at that moment, the call, when both ends keyed, when sync locked, the ACK that followed
Debrief	What changes for the next commanding pass

Times, what came back, what was done, in order. “Transient” and “attack” are conclusions; the record carries the NAK reason and the key state at the moment of the NAK.