The Department of Commerce, National Oceanic and Atmospheric Administration (NOAA) has an On ramp requirement for near-real-time satellite-based RO data from commercial vendors.

In order to respond to an ever-growing demand for environmental information, NOAA continually strives for an observing enterprise that is flexible, responsive to evolving technologies and economically sustainable, while continuing to be a leader and member of the global meteorological community. To help meet these goals, NOAA is interested in purchasing commercially-available Earth observing data that satisfy observational requirements at a lower cost than government-provided alternatives. Having previously evaluated satellite-based radio occultation (RO) data from multiple sources for use in weather models and other systems, NOAA seeks to enter into one or more contracts to purchase near-real-time satellite-based RO data from commercial vendors.

• Neutral Atmosphere Product Requirements:
  • RO soundings shall be collected as continuous dual-frequency open-loop measurements at either 50 Hz or 100 Hz
  • Data shall be provided only from instruments on satellites with an assigned World Meteorological Organization (WMO) satellite identifier
  • If applicable, the signal-to-noise ratio (SNR) conversion factor from dB-Hz to Volts/Volt (V/V) in a 1 Hz band shall be provided
  • The SNR of the stronger signal in a dual frequency signal pair, when averaged over HSL altitudes of 60 km to 80 km, shall be greater than 200 V/V in a 1 Hz band
  • The HSL altitudes of occultations shall span at least -150 km to 90 km
  • RO soundings shall be from GPS, GLONASS, or Galileo GNSS satellites
  • RO soundings shall be provided with concurrent precise orbit determination (POD) tracking data
  • POD tracking data shall include dual-frequency pseudo range, carrier phase, and SNR, as collected on-orbit in real time
  • POD tracking data shall include dual-frequency measurements recorded at 1 Hz or greater rate from a minimum of four GNSS satellites simultaneously for 95% of the POD data collection period
  • Every other orbit of each RO satellite from which data are provided shall be covered by POD tracking data at no less than 50% duty cycle with continuous arc length of at least 50 minutes per orbit
  • POD tracking data shall be from GPS satellites, plus optionally Galileo and/or GLONASS satellites
  • Navigation solutions calculated onboard the spacecraft shall be provided, including receiver clock offsets and time-tagged Earth-Centered-Earth-Fixed position and velocity
  • Navigation solution data shall be provided at intervals of 30 seconds or less
  • RO satellite attitude quaternions shall be collected concurrently with all POD and RO data at intervals of 30 seconds or less
  • All RO soundings shall have a latency of 140 minutes or less
  • The time of RO soundings shall be nearly uniformly distributed in time of day such that the quantity delivered in any six-hour period of the day, when averaged over 30 consecutive days, shall vary by less than a factor of two from any other six-hour period
  • At a minimum, the Contractor must have the capability to provide a daily count of at least 500 RO soundings, when averaged over any 30-day period, with no more than three days in any 30 day period falling beneath 400/day
  • Metadata shall include, at a minimum, for each satellite/instrument configuration:
    • Satellite mass, center of mass, external dimensions including any protruding appendages (e.g., solar array wings, antennae), satellite coordinate system geometry, POD and RO antenna reference point vectors relative to the center of mass and corresponding uncertainty estimates, antenna boresight vectors, and antenna fields of view
    • RO and POD antenna phase center offset and phase center variation measurements and corresponding uncertainty estimates, in ANTEX format (https://kb.igs.org/hc/en-us/articles/201096516-IGS-Formats)
• Space Weather Data
  • NOAA may require data that enable the generation of near-real-time ionospheric products for space weather applications
  • Data to be used for space weather products shall be suitable for retrieval of absolute slant TEC electron density profiles, S4 and sigma-phi indices
  • Data to be used for space weather products shall be delivered to NOAA with an observation latency of 22 minutes or less
  • The median daily latency of ionospheric data shall be 25 minutes or less
  • The sensing height range shall span HSL altitudes from 90 km to 800 km
  • The scintillation (amplitude and phase) indices shall be derived from phase measurements with a minimum sampling rate of 50 Hz
• Specific Geospatial Distributions
  • The number of RO soundings provided each day shall not vary by more than a factor of four (4) between any 30-degree latitude band
  • Within any 30-degree latitude band, the number of RO soundings provided each day within a 30 degree longitude section shall not vary by more than a factor of four (4) from any other 30 degree longitude section
• Neutral Atmosphere Data with Enhanced Signal-to-Noise Ratio
  • When required by NOAA, the SNR of the stronger signal in a dual frequency signal pair, when averaged over HSL altitudes of 60 km to 80 km, shall be greater than 1200 V/V in a 1 Hz band
• Specific Local Time Sampling
  • NOAA may include specific requirements on the distribution of local times of the RO soundings. When required in a Delivery Order, the local time of the delivered profiles shall be within the specified local time range or group of ranges. The extent of any local time ranges specified in a Delivery Order will be at least 1 hour
• Designated Satellites, Instruments or Modes
  • NOAA may limit the data in a Delivery Order to come from a specific predesignated list of satellites, instruments, or modes (for example, rising vs. setting occultations). Such a restriction would allow NOAA to coordinate data purchases with other Agencies and partners to avoid duplication of shared observational data