Features

• Identiﬁes and protects GPS systems

from spooﬁng and jamming

• Integrates seamlessly between existing

GPS antenna and GPS system

• Compatible with any GNSS antenna

that receives the L1 frequency

• Optional internal Rubidium Miniature

Atomic Clock (MAC) for holdover

• 1PPS and 10 MHz timing reference

inputs for extended holdover (for

example, connection of external

cesium reference)

• Redundant AC or DC power options

with power monitoring, load sharing,

and hitless switching

• Remote CLI in addition to secure and

easy-to-use web interface

• Blue

Sky

GNSS Firewall embedded

software is ﬁeld upgradeable with new

GPS validation rules

• Seamless integration with TimePictra

provides end-to-end management of

10s, 100s, or 1,000s of units from a

single server

• Blue

Sky

Performance Monitoring

integrated into TimePictra provides

GPS reception measurement and

visibility

Applications

• Wireline and wireless networks

• Utility and power grids

• Financial services

• Data centers

• Transportation networks

• Emergency services

Blue

Sky

GNSS Firewall

Protects GPS Systems Against Spooﬁng and Jamming Threats

The PNT Revolution

GPS revolutionized the world with

its ability to provide an accurate,

reliable, and cost-effective positioning,

navigation, and timing (PNT) service

with global coverage. Its rapid adoption

and widespread deployment enhances

our way of life, but has also led to a

dependency on GPS to maintain that

way of life. Critical infrastructure sectors

such as wireline and wireless networks,

power grids, ﬁnancial services, data

centers, and emergency services now

depend on PNT information delivered

by GPS.

Protecting Critical

Infrastructure

The vulnerability of GPS systems

to various signal incidents is well

documented. The rapid proliferation

of GPS systems has embedded these

vulnerabilities into critical national

infrastructures as well as corporate

infrastructures that rely on GPS-

delivered PNT for daily operations.

This widespread deployment of GPS

makes it impractical to replace all

ﬁelded GPS systems in a timely or

cost-effective manner.

Secure Firewall Overlay

The Blue

Sky

GNSS Firewall solves

the problem of protecting already

deployed systems by providing a

cost-effective overlay solution installed

between existing GPS antennas and

GPS systems. Similar to a network

ﬁrewall, the Blue

Sky

GNSS Firewall

protects systems inside the ﬁrewall

from untrusted sky-based signals

outside the ﬁrewall.

Contained within the Blue

Sky

GNSS

Firewall is a software engine that

analyzes the GPS signal. GPS signal

data is received and evaluated from

each satellite to ensure compliance

along with analyzing received signal

characteristics. This information is used

by the ﬁrewall to eliminate anomalous

GPS signals and provide a secure GPS

signal output to downstream GPS

systems.

Microsemi provides the Blue

Sky

Subscription, which delivers continuous

security updates and improvements

to the software engine. Details of the

service are provided in the Blue

Sky

Subscription datasheet.

Blue

Sky

Firewall Block Diagram

Multiple Levels of Resiliency

The Blue

Sky

GNSS Firewall provides the following two types of

GPS outputs.

Hardened GPS Output

Hardened GPS output is the most secure GPS output because

it provides a synthesized GPS signal isolated from the live-sky

environment. The hardened GPS output is not a copy of the

live-sky GPS signal and is only loosely based on information

received from the live-sky signal. Thus, a secure Blue

Sky

GPS

environment is created. When GPS incidents are detected,

the hardened GPS output continues to be available and relies

on the internal Rubiduium Miniature Atomic Clock (MAC) or

external frequency reference to maintain accuracy.

Validated GPS Output

Validated GPS output provides a copy of the actual GPS signal

being analyzed. When anomalous conditions are detected,

the validated GPS output is turned off to protect users from

potentially corrupted GPS signals. Once conditions are

deemed safe, the validated GPS output is turned back on.

Validated GPS includes copies of the L1, L2, and L5 signals

on a single output. This enables downstream systems that

use multiple GPS frequencies (such as SAASM or M-code) to

use the Blue

Sky

GNSS Firewall to provide an additional layer

of protection. Additionally, other constellation bands such as

Galileo, GLONASS, and Beidou are available on the validated

output. These signals are simply passed through but not

analyzed for spooﬁng along with the GPS signal.

Atomic Clock Holdover Options

The standard Blue

Sky

GNSS Firewall is equipped with a

high-quality crystal oscillator that maintains accuracy to within

nanoseconds when tracking GPS. When using the hardened

GPS output, the ﬁrewall can be equipped with a variety

of atomic clock options to provide holdover in the case of

complete GPS signal reception loss.

Blue

Sky

GNSS Firewall

Protects GPS Systems Against Spooﬁng and Jamming Threats

Rubidum Miniature Atomic Clock (MAC)

The ﬁrst option is upgrading the Blue

Sky

GNSS Firewall

with the Rubidium Miniature Atomic Clock (MAC), which can

provide excellent holdover of the hardened GPS signal output

for multiple days.

Microsemi’s MAC uses a unique physics package based on the

coherent population trapping (CPT) atomic clock. It consumes

less power and has broad temperature operation and longer

life than legacy lamp-based Rubidium clocks.

External References

Also available are external reference inputs that can be used

for holdover in place of the internal MAC. The Blue

Sky

GNSS

Firewall comes with 10 MHz and 1PPS reference inputs so

that an external reference such as Microsemi's 5071A or

TimeCesium products can be used for extended holdover in

the case of a complete loss of GPS reception for long periods

of time.

TimePictra with Blue

Sky

Performance

Monitoring Software

Management of wide scale deployment of Blue

Sky

GNSS

Firewall units is simpliﬁed using Microsemi’s TimePictra

management system. Included with the TimePictra platform is

the Blue

Sky

Performance Monitoring that enables a regional,

national, or global view of your timing infrastructure to provide

early alerting of threats before your timing network is adversely

impacted. Data metrics such as RF power, GPS position data,

GPS phase error, and satellite count can be collected from

each individual ﬁrewall and then plotted from the centralized

TimePictra platform. The Blue

Sky

Performance Monitoring

functionality is included as part of the BlueSky Subscription

service.

GPS Phase

Deviation

GPS Satellites

in View

GPS Signal

Strength