Chapter 4: Phase 1 - Data Format

The foundation of any interoperable system is a common language for representing information. In WIA-CONTACT-001, this foundation is provided by Phase 1: Data Format specifications. This chapter presents the complete data model for extraterrestrial signal detection, explains the JSON-LD serialization format, details the validation rules that ensure data integrity, and provides practical examples that illustrate proper implementation.

The data format specifications were developed through extensive consultation with radio astronomers, signal processing engineers, and data scientists from observatories worldwide. They represent a careful balance between expressiveness (capturing all relevant information) and practicality (remaining simple enough for widespread implementation). The format is designed to be both human-readable and machine-processable, supporting both interactive analysis and automated processing pipelines.

4.1 Data Model Overview

The WIA-CONTACT-001 data model centers on the Signal Detection Record (SDR), a comprehensive representation of a potential extraterrestrial signal. The SDR captures five categories of information that together provide a complete picture of the detection event:

• Identity: Unique identifiers, version information, and provenance data that trace the record's origin and history
• Signal Characteristics: Physical properties of the detected signal including frequency, bandwidth, power, modulation, and polarization
• Spatial Information: Celestial coordinates indicating where in the sky the signal originated, with uncertainty estimates
• Temporal Properties: When the signal was detected, its duration, and any periodicity or recurrence patterns
• Contextual Metadata: Information about the detecting facility, instrument configuration, and observing conditions

Each category is represented as a nested object within the SDR, with required and optional fields clearly specified. This modular structure allows for incremental refinement as more information becomes available during the verification process. A tentative detection can be submitted with minimal required fields, then updated as additional observations provide more detail.

4.2 Signal Detection Record (SDR) Schema

The following JSON schema defines the complete structure of a Signal Detection Record. This example shows all major fields with representative values:

{
  "@context": "https://wia.standards.org/contact-001/v1",
  "@type": "SignalDetectionRecord",
  "id": "sdr:2025-12-29-GBT-001",
  "version": "1.0.0",
  "created": "2025-12-29T14:30:00Z",
  "modified": "2025-12-29T15:45:00Z",

  "signal": {
    "frequency": {
      "center": 1420405751.768,
      "bandwidth": 0.5,
      "unit": "Hz",
      "frame": "barycentric",
      "driftRate": 0.0023
    },
    "power": {
      "snr": 15.7,
      "flux": 1.2e-26,
      "unit": "W/m²/Hz",
      "spectralDensity": -220.5
    },
    "modulation": {
      "type": "narrowband",
      "characteristics": ["continuous", "stable"],
      "encoding": null
    },
    "polarization": "circular-right"
  },

  "source": {
    "position": {
      "ra": "19h25m12.34s",
      "dec": "+21d45m32.1s",
      "frame": "ICRS",
      "epoch": "J2000"
    },
    "uncertainty": {
      "ra": 0.5,
      "dec": 0.5,
      "unit": "arcsec",
      "confidence": 0.95
    },
    "properMotion": null,
    "distance": null
  },

  "temporal": {
    "detected": "2025-12-29T14:25:33.123Z",
    "duration": 72.5,
    "unit": "seconds",
    "recurring": false,
    "period": null,
    "ephemeris": null
  },

  "context": {
    "facility": "GBT",
    "instrument": "L-band receiver",
    "observer": "Dr. Sarah Chen",
    "conditions": {
      "rfiLevel": "low",
      "weather": "clear",
      "solarActivity": "quiet"
    }
  },

  "status": "unverified",
  "confidence": 0.72,
  "threatLevel": "unknown"
}
        

4.3 Core Data Types

4.3.1 Frequency Specification

Frequency values are represented with high precision to enable accurate signal identification and tracking. The center frequency is specified in Hertz as a floating-point number with at least 9 significant digits. This precision is essential because narrowband extraterrestrial signals could have bandwidths of 1 Hz or less, and even small frequency errors could cause a verification observation to miss the signal entirely.

Table 4.1: Frequency Data Fields

Field	Type	Required	Description
center	number	Yes	Center frequency in Hz (9+ significant digits)
bandwidth	number	Yes	Signal bandwidth in Hz
unit	string	Yes	Must be "Hz"
frame	string	No	Reference frame: topocentric, barycentric, rest
driftRate	number	No	Doppler drift in Hz/s (crucial for ETI detection)

The reference frame is particularly important for verification. A signal observed at one frequency from Earth will appear at a slightly different frequency when corrected to the solar system barycenter, due to Earth's orbital motion. The standard default is topocentric (as observed), but barycentric values enable direct comparison between observations made at different times.

4.3.2 Celestial Position

Source positions use the International Celestial Reference System (ICRS) by default, with right ascension and declination specified in either standard sexagesimal notation (hours/degrees, minutes, seconds) or decimal degrees. Both formats are accepted; the system automatically converts as needed.

Uncertainty estimates are mandatory for position data. These estimates enable verification observations to define appropriate search regions and allow statistical assessment of whether independent detections are consistent with a common source. The standard uses elliptical uncertainty regions characterized by semi-major axis, semi-minor axis, and position angle.

4.3.3 Temporal Information

All timestamps use ISO 8601 format with UTC timezone and millisecond precision where available. The detection timestamp indicates when the signal was first identified in the data stream (which may differ from when the data was recorded, in the case of archived data analysis). Duration specifies how long the signal was continuously observed.

For recurring or periodic signals, additional fields capture the recurrence pattern. This information is valuable for scheduling verification observations—if a signal repeats every 24.7 hours, verification attempts can be timed to coincide with expected transmissions.

4.3.4 Power and Signal-to-Noise

Signal strength is characterized by both signal-to-noise ratio (SNR) and absolute flux density. SNR provides a relative measure that is directly relevant to detection threshold comparisons—a signal with SNR of 10 is clearly detected, while one with SNR of 3 is marginal. Flux density in physical units (W/m²/Hz or Jansky) enables absolute calibration and comparison across different instruments with different sensitivities.

4.4 Metadata Structure

Contextual metadata provides essential information for interpreting the detection. The facility identifier must match a registered observatory in the WIA facility registry. This registry contains detailed information about each facility's capabilities, including telescope diameter, receiver systems, geographic location, and scheduling contacts.

"context": {
  "facility": {
    "id": "GBT",
    "name": "Green Bank Telescope",
    "location": {
      "latitude": 38.4330,
      "longitude": -79.8397,
      "elevation": 807,
      "timezone": "America/New_York"
    },
    "telescope": {
      "diameter": 100,
      "type": "single-dish",
      "mount": "alt-az"
    }
  },
  "instrument": {
    "name": "L-band receiver",
    "frequencyRange": [1150e6, 1730e6],
    "backend": "VEGAS",
    "resolution": 1.0,
    "polarizations": ["LCP", "RCP"]
  },
  "observation": {
    "mode": "tracking",
    "integration": 60,
    "calibrated": true,
    "calibrationMethod": "noise-diode"
  },
  "conditions": {
    "rfiLevel": "low",
    "weather": "clear",
    "solarActivity": "quiet",
    "ionosphericConditions": "stable"
  }
}
        

4.5 Validation Rules

All SDR submissions must pass multi-level validation before acceptance into the system. This validation ensures data quality and prevents common errors that could compromise verification efforts.

Level 1 - Schema Validation: The record must conform to the JSON schema, with all required fields present and correctly typed. Missing required fields, type mismatches (string where number expected), and malformed JSON all trigger Level 1 errors.

Level 2 - Range Validation: Numeric values must fall within physically plausible ranges. Frequencies must be positive. SNR must be greater than 1 (otherwise, what was detected?). Celestial coordinates must be valid (RA between 0 and 360 degrees, Dec between -90 and +90 degrees). Duration cannot exceed the time between detection and submission.

Level 3 - Consistency Validation: Related fields must be internally consistent. If polarization is "circular-right", the instrument must support circular polarization. The frequency must fall within the instrument's frequency range. The observation duration cannot exceed the facility's maximum track time for the source position.

Level 4 - Reference Validation: Identifiers referencing external entities must correspond to valid registry entries. Facility IDs, instrument types, and observer credentials are all verified against authoritative databases.

Table 4.2: Common Validation Errors and Resolutions

Error Code	Level	Description	Resolution
SDR-001	1	Missing required field	Add the required field with a valid value
SDR-002	1	Invalid data type	Ensure field value matches expected type
SDR-003	2	Value out of range	Check physical plausibility of value
SDR-004	4	Unknown facility ID	Register facility or correct ID
SDR-005	3	Temporal inconsistency	Check timestamp ordering and durations
SDR-006	3	Frequency outside instrument range	Verify instrument configuration

4.6 Example Records

Example 1: Narrowband Continuous Signal

This example shows a typical narrowband signal detection at the hydrogen line frequency—the classic "water hole" target for SETI searches:

{
  "@context": "https://wia.standards.org/contact-001/v1",
  "@type": "SignalDetectionRecord",
  "id": "sdr:2025-12-29-ATA-042",
  "signal": {
    "frequency": {
      "center": 1420405751.768,
      "bandwidth": 0.1,
      "unit": "Hz",
      "driftRate": 0.0023
    },
    "power": { "snr": 12.3, "flux": 8.5e-27 },
    "modulation": { "type": "narrowband", "characteristics": ["continuous"] }
  },
  "source": {
    "position": { "ra": 82.5, "dec": -12.3, "frame": "ICRS" },
    "uncertainty": { "ra": 1.0, "dec": 1.0, "unit": "arcsec" }
  },
  "temporal": { "detected": "2025-12-29T10:15:00Z", "duration": 120 },
  "context": { "facility": "ATA", "instrument": "feed-42" },
  "status": "unverified"
}
        

Example 2: Pulsed Periodic Signal

This example shows a pulsed signal with regular periodicity—potentially a beacon transmission:

{
  "@context": "https://wia.standards.org/contact-001/v1",
  "@type": "SignalDetectionRecord",
  "id": "sdr:2025-12-29-Parkes-007",
  "signal": {
    "frequency": { "center": 2800000000, "bandwidth": 1000, "unit": "Hz" },
    "power": { "snr": 8.7 },
    "modulation": { "type": "pulsed", "pulseWidth": 0.005, "period": 1.337 }
  },
  "source": {
    "position": { "ra": "12h30m45s", "dec": "-45d30m00s", "frame": "ICRS" }
  },
  "temporal": {
    "detected": "2025-12-29T08:00:00Z",
    "duration": 3600,
    "recurring": true,
    "period": 86400
  },
  "status": "verification-requested"
}
        

4.7 Migration from Legacy Formats

Many existing SETI programs use proprietary data formats developed over decades. WIA-CONTACT-001 provides migration tools to convert common legacy formats to the standard SDR format, enabling historical data to be integrated into the global network.

Converters are available for: SETI@home work units (Berkeley BOINC format), Breakthrough Listen filterbank and HDF5 formats, SERENDIP spectral data, ATA antenna array outputs, and generic FITS files with appropriate metadata extensions.