Deliverable 6.5: Annual status report on the performance specification activity

The integrated performance specification is kept under continuous review with regular iterations to incorporate developments in the other Work Packages. The current version of the document is posted annually as a deliverable of Work Package 6.

The EISCAT_3D facilities will comprise one transmit/receive core site and four distant, primarily receive sites equipped with antenna arrays, supporting instruments, platforms for movable equipment and high data-rate Internet connections. The receive sites will be arranged at a pair of closer locations to the core to provide high resolution E-region vector drift measurements and another pair of locations spaced further from the core for F-region vector coverage over a larger region. The two pairs of receive sites with will be located at baseline distances within roughly 90 km ≤ d ≤ 280 km of the core site. The core site with full transmitting and receiving capabilities will be located within roughly 100 km of a point at 69 degrees North and 20.5 degrees East, well situated for auroral zone research.

The mono-static core array will consist of antenna elements having transmitting and receiving capabilities as well as relatively closely located antennas to support aperture synthesis imaging for probing within the transmitted beam. Each element will have full polarization control on transmit and full polarization measurements on receive. The polarization measurement capability will also be available at all receive sites. Synchronization between the subsystems will be handled via a combination of short latency internet connections, local GPS-based real-time clocks, stable clock oscillators at each site, and a high-accuracy clock distribution system at each site (most likely based on an extension of the IEEE-1588 protocol). Each site will also contain sufficient processing capacity for digital beam forming, local storage of intermediate measurement products, and processing capacity for near real-time plasma parameter extraction.

The entire system will be configured for unattended remote operations, though there may be the need for a very small staff, especially at the core, for safety reasons. The sites will, however, also have limited infrastructure to support scientific and technical visitors for research campaigns.

The core site will comprise:

  • Phased-array, polarization-flexible antenna with on the order of 10,000 elements (actual number of antenna elements based on optimization of system costs)
  • Distributed RF signal generation exciters, two per antenna element, amplitude and phase capable
  • Distributed RF power amplifiers, 2×500 W per antenna, amplitude and phase modulation capable
  • Distributed transmit/receive switching
  • Distributed low noise amplifiers, total added noise goal is <50 K
  • Receive-only outlier elements for narrow receiving beams and in-beam interferometry
  • Beam forming system
  • Time and frequency synchronization equipment
  • Digital signal processing equipment (in addition to beam forming)
  • Built-in test and monitoring equipment
  • System calibration equipment
  • Power control and distribution equipment

The total size of the central site will exceed 1 km, given that the dense inner core of antennas will be accompanied by a sparsely distributed array of outlying antennas. The dense inner core will require approximately 70 m × 70 m of space, with an additional buffer for safety.

The remote sites will comprise:

  • Phased-array, polarization-flexible antenna with on the order of 10,000 elements (actual number of antenna elements based on optimization of system costs)
  • Distributed low noise amplifiers, total added noise goal is <50 K
  • Beam forming system
  • Time and frequency synchronization equipment
  • Digital signal processing equipment (in addition to beam forming)
  • Built-in test and monitoring equipment
  • System calibration equipment
  • Power control and distribution equipment

The transmitter parameters are:

  • Centre frequency near 233 MHz
  • Peak output power: 1000 W per antenna element, totaling approximately 10 MW
  • Instantaneous: 3 dB power bandwidth >5 MHz
  • Pulse length: 0.5–3000 microseconds
  • Duty cycle: 0-25%
  • Interpulse period: > 100 microseconds (fully flexible pulse sequences)
  • Capability to transmit arbitrary phases and amplitudes
  • Stable gain and delays over the specified temperature range

The receiver parameters are:

  • Centre frequency 233 MHz (or centered around transmitter frequency)
  • Instantaneous bandwidth: +/- 15 MHz at core site, preferably also at other sites at least +/- 5 MHz
  • Overall added noise temperature (above sky noise): <50 K referenced
  • Spurious-free dynamic range: >70 dB

Computational system should be able to extract data and calculate at least 100 beams simultaneously.

The system parameters will be selected such that, over the multi-static field-of-view, the resolution along the transmitted beam direction(s) can be made better than 100 m at any altitude and the horizontal (transverse) –3 dB resolution at 100 km altitude is better than 100 m. The beam generated by the central core transmit/receive antenna array will be steerable out to a maximum zenith angle of the order of 40 degree (60 degree with lower performance) in all azimuth directions. The beam from the central core antenna array will be steerable into any new pointing direction on timescale better than 1 microsecond through coordinated switching of the exciters.

Environmental considerations, maintenance costs as well as possible malfunction during ice and snow coverage need to be considered for antenna design. Changes in performance due to ice and snow coverage need to be within a range that can be compensated by adjusting the measurement parameters. Ideally the antenna performance does not require a solid ground plane. The configuration shall be as insensitive as possible to snow conditions, particularly with respect to snow accumulation.

The sites shall be equipped with facilities for Optical Cameras, Ionosondes and Data Storage. Sites should be prepared over a range larger than what is needed for initial instrumentation in order to have the space for further instruments and in order for further construction works not disturbing measurements. Site infrastructure needs to account for shielded mitigation of RF interference, especially at the core but also at the remote locations.

Optical Cameras
Support for basic optical instrumentation at the core and selected distant sites will allow the observation of auroral or airglow emissions and Doppler shifts due to mesospheric and thermospheric neutral winds at the time and location of the radar observations. This can be facilitated by installing CCD equipped standard cameras with filter change capacity near the core site and at several distant sites, as well as a Fabry Perot imaging spectrometer at the core. Facilities for these cameras need to be available close enough to minimize and mitigate parallax issues.
Ionosondes
Digital ionosondes at all sites will support the radar measurements and broaden the parameters obtained from continuous coverage.
Data Storage
Data storage and communication systems shall be located at, or close to, each site.