Galileo Gloves Come Off: Military After All

The European Parliament on July 10 explicitly recognized the need for Galileo to serve the European Union’s defense and security — a change from its earlier stance.

Galileo proponents originally envisioned the European GNSS as existing completely in and for the civilian realm; a key argument for Galileo had been the U.S. military’s administration of GPS. In the past, Parliament rejected resolutions or legislation that hinted at a military role for Galileo. But with wholly public funding now fixed for the project, Parliament recognized the role of Galileo to European defense and military interests in space.

Further, a recently completed 18-month survey conducted for the Galileo Supervisory Authority found that half of all users of the Galileo encrypted signal will be military customers, with the other half made up of law enforcement agencies and emergency response services. The survey also found that more than two-thirds of the prospective users of Galileo’s Public Regulated Service (PRS) either have or expect to have access to the military code of the U.S. GPS network.

Defense Report. By a large majority (483-99-20), the body adopted a security and defense subcommittee “own-initiative” report, effectively making it a resolution. The report underlines “the need for space assets in order that the political and diplomatic activities of the European Union may be based on independent, reliable and complete information.”

It recognizes “the necessity of Galileo for autonomous European Security and Defense Policy (ESDP) operations, for the Common Foreign and Security Policy (CFSP), for Europe’s own security, and for the Union’s strategic autonomy.” The report urges EU member states to ensure the interoperability of observation and reconnaissance systems and “recommends the urgent conclusion of agreements between the EU Satellite Center and EU member states to provide imagery to ESDP operation and force commanders.”

The report decried militarization of space and Europe’s lack of an early-warning system for ballistic missile launches. “Under no circumstances should European space policy contribute to the overall militarization and weaponization of space.” Parliament called on the European Union to “promote a conference to review the Outer Space Treaty, with the aim of strengthening it and expanding its scope to prohibit all weapons in space” and called on the international community “to refrain from using offensive equipment in space.”The report also urges Europe to set up an operational budget for European space assets, putting them under the European community budget. “As experience has shown, large-scale common projects cannot be properly managed when 27 different national budget authorities applying the principle of fair return are involved.”

GIOVEs A and B Double-Differenced

Researchers at the Netherlands’ Delft University of Technology (TU Delft) have produced the first double-difference measurements from Galileo satellite signals, tracking GIOVE-A and GIOVE-B satellites with Septentrio GNSS receivers.

TU Delft researchers made the measurements during a 1.5-hour window of simultaneous visibility of both GIOVE-A and GIOVE-B on July 6. This enabled them to collect simultaneous ranging measurements of the L1 open-source signals broadcast by the two Galileo satellites, as well as signals from 12 GPS satellites and two EGNOS satellites.

“With Galileo pseudorange measurements taken by AsteRx1 receivers, using the binary offset carrier (BOC) modulation on the L1 frequency, the Galileo double difference carrier phase cycle ambiguity could be precisely estimated, and consequently fixed to an integer value, with large confidence,” according to Christiaan Tiberius and Hans van der Marel.

They set up two Septentrio 24-channel AsteRx1 receivers with a short baseline to perform pure Galileo double-difference calculations. Such measurements are key to real-time kinematic (RTK) applications; Septentrio suggested that the Delft tests pave the way for multi-constellation RTK receivers.

The researchers began tracking GIOVE-B on June 10, when the satellite was still undergoing payload configuration, but in a limited time span, ranges could be measured using the transmitted signal in the L1 band with experimental firmware from Septentrio.

First analyses show the ranging accuracy is better than with GPS, according to the TU Delft researchers.

EPOCHWISE AMBIGUITY estimate between GIOVE-A and
GIOVE-B. The overall ambiguity is fixed, with large
confidence, to the integer value –9.

Software Future for GNSS

The International GNSS Service (IGS) has published a white paper on the future use of GNSS for high-accuracy applications. A federation of more than 200 agencies that pool resources and GPS and GLONASS data from a network of more than 350 permanent, continuously operating, geodetic-quality monitoring stations, the IGS foresees many changes over the next few years, particularly for hardware. A PDF of “Considerations for Future IGS Receivers” is available.

“The new GNSS signals that will come online over the next decade will render current IGS receivers obsolete,” assert the paper’s authors, Todd Humphreys, Larry Young, and Thomas Pany, “so it is prudent to examine receiver options going forward. [Also,] the push to improve the accuracy of IGS products beyond current limits demands greater accuracy in the models used to describe receiver measurements. As a result, the IGS must demand from vendors more transparency into receiver firmware or adoption of user-specified algorithms.”

The body of the paper considers modernized GNSS signals and their benefits for the IGS; surveys the range of expected receiver capability; considers current and future commercial geodetic-quality receivers; considers software GNSS receivers as an alternative to less reconfigurable traditional receivers; and lays out the authors’ recommendations to the IGS. This includes a suggested schedule for the evolution of minimum IGS receiver requirements, which might be met by either future commercial or possibly non-commercial options, according to the organization.

GPS World’s contributing editor for survey and construction, Eric Gakstatter, interviewed the authors and provided an account in his July 16 newsletter. Here is a brief excerpt:

EG: What is the major attraction of software receivers?

TH: From the point of view of the IGS, the major attractions are flexibility and transparency. The IGS’s goal is to deliver gold-standard GNSS orbits, clocks, reference frame positions, and iono/tropo maps. For this, we need transparency into receiver operation so that we can better model the statistics of the receiver products that we use. Better yet, we’d like to implement our own specialized tracking loops and other specialized receiver features. Software receivers offer us this transparency and flexibility.

Although it probably takes a back seat to transparency and flexibility, price is certainly an attraction. For example, the ASTRA software receiver mentioned in the paper is planned to be offered for around $1,200 (hardware) plus $200 or so per receiver for a software maintenance contract. This is about 10 times less expensive than the traditional receivers that the IGS buys. If ASTRA and others can really deliver at such reduced prices, you may see an exciting densification of IGS sub-networks for tropospheric and ionospheric study.

EG: Are GNSS software receivers technically able to replace traditional receivers in fixed GNSS infrastructure environments, such as CORS, IGS, JPL, SoPAC?

TH: Absolutely. The JPL BlackJack receiver is arguably the best-performing GPS receiver on the planet today, and it’s essentially a software receiver with an FPGA-based correlation engine. I suspect that the reference-frame receivers sold by some traditional vendors are, in fact, software receivers in the BlackJack mold. I predict a market-wide convergence toward FPGA/DSP-based software GNSS receivers over the next decade as the FPGS/DSP price-per-transistor count continues to fall.