Attachment 2_ Preliminary Draft Radar Next C-Band Requirements.pdf
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This is a preliminary draft requirements document for the Radar Next program, issued by the Department of Commerce's National Oceanic and Atmospheric Administration (NOAA) and National Weather Service (NWS) dated May 26, 2026. The document outlines C-Band radar system requirements intended to facilitate industry discussions regarding implementation as part of the Radar Next solution. The requirements are presented as placeholder values derived from the current NEXRAD WSR-88D specification and are acknowledged as potentially infeasible for C-Band systems, serving as a starting point for stakeholder engagement.
The Minimum Viable Product (MVP) shall produce six base weather products: Reflectivity, Radial Velocity, Spectrum Width, Differential Reflectivity, Correlation Coefficient, and Differential Phase in NEXRAD Level II formatted data. The system must provide remote Command and Control capabilities, comply with FISMA High and DHS High Value Asset requirements, and maintain performance integrity across both Continental United States (CONUS) and Outside Continental United States (OCONUS) deployments. Key technical specifications include reflectivity range of ≥460 kilometers at -32 to 94.5 dBz with 0.5 dBz resolution and <1 dBZ accuracy; radial velocity range of ≥300 kilometers with ±26.0 meters per second maximum unambiguous velocity; spectrum width accuracy of 0.95 meters per second; differential reflectivity range of ≥300 kilometers with <0.4 dB accuracy; correlation coefficient range of 0.2 to 1.1 with <0.006 accuracy; and differential phase range of 0 to 360 degrees with <2.5 degree accuracy. The antenna must be a single pencil beam with <1 degree half-power beamwidth in both horizontal and vertical channels, ≥66 dB first sidelobe suppression, and ≥40 dB cross-polarization isolation. The system shall operate in Simultaneous Transmit Dual-Pol/Simultaneous Receive (STSR) configuration with clutter filtering attenuation ≥50 dB and detection sensitivity of ≤-9.5 dBZe at 50 kilometers. Operational requirements specify ≥95% availability with continuous 24/7/365 operation, <10 second data latency to NWS ingest point (≤3 seconds average), MTBF ≥800 hours, and maximum outage duration of 24 hours (CONUS) or 72 hours (OCONUS). Environmental specifications require operation in sustained winds of ≥63 meters per second, altitudes up to 3,300 meters, temperatures from -40°C to +50°C (operating) and -62°C to +60°C (non-operating), 15-95% relative humidity, rainfall rates up to 300 millimeters per hour, snow/ice loading of 235 kilograms per square meter, and compliance with salt-fog and fungus exposure standards. The pedestal must provide continuous 360-degree azimuth motion and -3 to +110 degree elevation movement with pointing resolution ≤0.0439 degrees, azimuth rotation rates ≥36 degrees per second, and elevation velocity ≥30 degrees per second. The document includes seven additional vendor questions addressing water tower installation concerns, UPS power solutions, backup power switchover, grounding/lightning protection standards, operating environment compliance, maintenance and calibration procedures, and cross-polarization isolation capabilities.
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Pre-Decisional / Draft Radar Next Industry Day
Attachment 2: Preliminary Draft Radar Next C-Band Requirements
Department of Commerce (DOC) / National Oceanic and Atmospheric Administration (NOAA) / National Weather Service (NWS) Preliminary C-Band Requirements for Radar Next May 26, 2026
Introduction / Context: The requirements in the table below reflect preliminary, draft C-Band requirements for the Radar Next program. These requirements are not intended to be the complete set of C-Band requirements, but the identification of key requirements to facilitate discussions regarding the use of C-Band radar systems as part of the Radar Next solution. Additionally, many of the values specified in these C-Band requirements are taken directly from the current Next Generation Weather Radar (NEXRAD) Weather Surveillance Radar 1988-Doppler (WSR-88D) specification. While these values may not be feasible for C-Band radar systems, they provide placeholder values representing a starting point for discussions with industry and other stakeholders.
Requirement Additional Notes / Qualifiers
Minimum Viable Product (MVP)
1 The Radar Next system shall produce the 6 base weather products for Reflectivity, Radial Velocity, Spectrum Width, Differential Reflectivity, Correlation Coefficient, and Differential Phase.
2 The Radar Next system shall provide the capabilities identified in all sections below.
3 The Radar Next system shall provide a Command and Control function that can be physically housed and operated in a separate location from the radar sensor.
4 The Radar Next system shall comply with Federal
Information Security Modernization Act (FISMA)
High requirements.
5 The Radar Next systems shall comply with
Department of Homeland Security High Value Asset
(HVA) requirements.
6 The Radar Next system shall have no degradation of system performance and no damage to the radar system, i.e., no reduction in data quality and no loss of calibration, per the Environmental Requirements section below.
7 By withstanding the environmental factors identified in the Environmental Requirements section below, the radar system shall sustain no immediate damage and is capable of returning to
Attachment 2: Preliminary Draft Radar Next C-Band Requirements
Requirement Additional Notes / Qualifiers its previous level of operation upon the removal of the environmental factor.
Coverage
1 The Radar Next system shall be implemented in
Continental United States (CONUS).
2 The Radar Next system shall be implemented
Outside Continental United State (OCONUS).
Weather Forecasting and Analysis Requirements: 6 Base
Products and Product Specifications
1. At a minimum, the C-Band radar systems shall provide NEXRAD Level II formatted data to the NWS ingest point.
2. As additional detail for the 6 Base Products is developed, clarification will be provided to indicate that Level 2 products will include range correction.
1 The Radar Next system shall provide reflectivity measurements.
Additional requirements for dwell/PRT may be added at a later date.
2 The Radar Next system shall have a reflectivity radial range of >= 460 kilometers.
3 The Radar Next system shall have a reflectivity data range from -32 dBz to 94.5 dBz.
4 The Radar Next system shall provide a reflectivity measurement with a resolution of 0.5 dBz.
5 The Radar system shall provide a reflectivity measurement with an accuracy of < 1 dBZ.
The following qualifiers apply to the accuracy of the reflectivity measurement:
(1) Reflectivity measurement accuracy assumes a true spectrum width of 4.0 meters per second.
(2) Reflectivity measurement accuracy valid at a Signal-to-Noise Ratio (SNR) of >= 10 dB.
(3) Means shall be provided to limit the differential reflectivity bias to an uncertainty of +/- 1 dB (threshold/objective) within a 95% confidence level
6 The Radar Next system shall provide radial velocity measurements.
7 The Radar Next system shall have a radial velocity
Attachment 2: Preliminary Draft Radar Next C-Band Requirements
Requirement Additional Notes / Qualifiers range of >= 300 kilometers.
8 The Radar Next system shall have a maximum unambiguous radial velocity of <= -26.0 meters per second and >= +26.0 meters per second.
While not stated, the maximum unambiguous range associated with this unambiguous velocity is 75 kilometers. This requirement represents degraded performance relative to the WSR-88D, which has a maximum unambiguous velocity closer to 34 meters per second with an unambiguous range close to
115 kilometers.
9 The Radar Next system shall provide a radial velocity measurement with a resolution of 0.5 meters per second, as measured natively.
10 The Radar Next system shall provide a radial velocity measurement, including accounting for quantization errors, with a data accuracy of 1.0 meters per second, as measured natively.
The following qualifiers apply to the accuracy of the radial velocity measurement:
(1) Radial velocity measurement accuracy assumes a true spectrum width of 4.0 meters per second.
(2) Radial velocity measurement accuracy valid at a SNR of >= 8 dB.
11 The Radar Next system shall provide spectrum width measurements.
12 The Radar Next system shall have a spectrum width radial range of >= 300 kilometers.
13 The Radar Next system shall provide a spectrum width measurement with a data range >= 26 meters per second.
NOTE: Any calculated value above 10 meters per second shall be capped at 10 meters per second in the Level II data.
14 The Radar Next system shall provide a spectrum width measurement, including accounting for quantization errors, with a data accuracy of .95 meters per second.
The following qualifiers apply to the accuracy of the spectrum width measurement:
(1) Spectrum width measurement accuracy assumes a true spectrum width of 4.0 meters per second.
(2) Spectrum width measurement accuracy valid at a signal to noise ratio (SNR) of >= 8 dB.
15 The Radar Next system shall provide differential reflectivity measurements.
16 The Radar Next system shall have a differential reflectivity radial range of >= 300 kilometers.
Question to Industry: How do you correct raw
ZDR measurements?
17 The Radar Next system shall have a differential
Attachment 2: Preliminary Draft Radar Next C-Band Requirements
Requirement Additional Notes / Qualifiers reflectivity data range of -13 dB to +20 dB.
18 The Radar Next system shall provide a differential reflectivity measurement with a resolution of
0.00625 dB.
19 The Radar Next system shall provide a differential reflectivity measurement with an accuracy of < .4 dB.
The following qualifiers apply to the accuracy of the differential reflectivity measurement:
(1) Differential reflectivity measurement accuracy assumes a true spectrum width of
2.0 meters per second.
(2) Differential reflectivity measurement accuracy valid at a SNR of >= 20 dB.
(3) Differential reflectivity measurement accuracy valid at a correlation coefficient of >=
0.99.
(4) Differential reflectivity measurement accuracy valid with a dwell time of 50 ms.
(5) Means shall be provided to limit the differential reflectivity bias to an uncertainty of +/- 0.2 dB (threshold), +/- 0.1 dB (objective) within a 95% confidence level
20 The Radar Next system shall provide correlation coefficient measurements.
21 The Radar Next system shall have a correlation coefficient radial range >= 300 kilometers.
22 The Radar Next system shall have a correlation coefficient data range of .2 to 1.1.
Question to Industry: How do you generate your moments?
23 The Radar Next system shall provide a correlation coefficient measurement with a resolution of
.00333.
24 The Radar Next system shall provide a correlation coefficient measurement with an accuracy < 0.006.
The following qualifiers apply to the accuracy of the correlation coefficient measurement:
(1) Correlation coefficient measurement accuracy assumes a true spectrum width of
2.0 meters per second.
(2) Correlation coefficient measurement accuracy valid at a SNR of >= 20 dB.
(3) Correlation coefficient measurement accuracy valid at a correlation coefficient of >=
Attachment 2: Preliminary Draft Radar Next C-Band Requirements
Requirement Additional Notes / Qualifiers
0.99.
(4) Correlation coefficient measurement accuracy valid with a dwell time of 50 ms.
25 The Radar Next system shall provide differential phase measurements.
Question to Industry: Provide details on delivered PhiDP, i.e., is it raw measured differential phase, system-phase-corrected
PhiDP, unfolded PhiDP, or a
NEXRAD-compatible wrapped product?
26 The Radar Next system shall have a differential phase radial range >= 300 kilometers.
27 The Radar Next system shall have a differential phase data range of 0.0 to 360.0 degrees.
28 The Radar Next system shall provide a differential phase measurement with a resolution of 0.35 degrees.
29 The Radar Next system shall provide a differential phase measurement with an accuracy of < 2.5 degrees.
Question to Industry: Describe how you conduct system differential phase calibration and how PhiDP is initialized and corrected to ensure the required accuracy.
NOTE: The following qualifiers apply to the accuracy of the differential phase measurement:
(1) Differential phase measurement accuracy assumes a true spectrum width of 2.0 meters per second.
(2) Differential phase measurement accuracy valid at a SNR of >= 20 dB.
(3) Differential phase measurement accuracy valid at a correlation coefficient of >= 0.99.
(4) Differential phase measurement accuracy valid with a dwell time of 50 ms.
30 The Radar Next system shall operate in a
Simultaneous Transmit Dual-Pol / Simultaneous
Receive (STSR) Dual-Pol configuration.
31 The Radar Next system antenna shall be a single pencil beam, where the main lobe is defined as the region within the half-power beamwidth in the
Attachment 2: Preliminary Draft Radar Next C-Band Requirements
Requirement Additional Notes / Qualifiers horizontal and vertical polarizations.
32 The Radar Next system antenna shall have a half-power beamwidth of < 1 degree in the horizontal channel. If utilizing a phased array antenna, the antenna shall have a half-power beamwidth of < 1 degree across all scan angles in the horizontal channel.
33 The Radar Next system antenna shall have a half-power beamwidth of < 1 degree in the vertical channel. If utilizing a phased array antenna, the antenna shall have a half-power beamwidth of < 1 degree across all scan angles in the vertical channel.
34 The Radar Next system antenna's main lobes in the horizontal and vertical polarizations, down to 20 dB below the peaks, shall be within 1 dB of each other.
If utilizing a phased array antenna, the antenna's main lobes in the horizontal and vertical polarization, down to 20 dB below the peaks, shall be within 1 dB of each other across all scan angles in the horizontal channel.
35 The Radar Next system antenna shall have the following two-way sidelobe levels:
(1) The first two-way sidelobe shall be >= 66 dB below the main lobe level.
(2) Between +/- 2 and +/- 12 degrees from the main lobe peak, the two-way sidelobe level shall lie below a straight line connecting 66 dB below the main lobe at +/- 2 degrees, and 100 dB below the main lobe at +/- 12 degrees.
(3) Between +/- 12 and +/- 180 degrees, the two-way sidelobe level shall be >= 100 dB below the main lobe level.
(4) Between +/- 12 and +/- 180 degrees, the peak of an individual two-way sidelobe exceeding 100 dB below the main lobe level may be averaged with sidelobes within 2 degrees surrounding the offending sidelobe, provided the averaged value
Attachment 2: Preliminary Draft Radar Next C-Band Requirements
Requirement Additional Notes / Qualifiers does not exceed 100 dB below the main lobe level.
(5) Between +/- 12 and +/- 180 degrees, no single two-way sidelobe shall be > 88 dB below the main lobe level.
36 The Radar Next system antenna shall have cross-polarization isolation in the main lobes >= 40 dB. If utilizing a phased array antenna, the antenna shall have cross-polarization isolation in the main lobe of >= 40 dB across all scan angles.
37 All data shall be disseminated with an azimuth resolution of 0.5 degrees (assumed use of “super resolution” techniques).
38 All data shall be disseminated with a range resolution no greater than 300 meters.
Weather Forecasting and Analysis Requirements:
Clutter Filtering and Data Placement Error
1 The Radar Next system shall provide clutter filtering and data placement error resolution.
Question to Industry: Describe how you perform clutter filtering.
2 Clutter filtering shall be performed with an attenuation of >= 50 dB.
3 Clutter filter power removed shall be provided in
Level 2 data products .
4 Data placement error shall be < 50 m (threshold), <
1 m (objective).
5 Clutter filtering shall be performed for stationary targets prior to the estimate of the 6 base products.
6 Clutter filtering shall be performed for point targets
(e.g., aircraft) prior to transmitting Level 2 data to the ingest point.
Minimum Sensitivity
1 The Radar Next system shall meet a minimum detection sensitivity of <= ‑9.5 dBZe at
50 kilometers.
2 The Radar Next system shall meet a minimum detection sensitivity of <= ‑2.2 dBZe at
Attachment 2: Preliminary Draft Radar Next C-Band Requirements
Requirement Additional Notes / Qualifiers
50 kilometers when a rain rate of 100 millimeters per hour is present.
3 The Radar Next system shall meet a minimum detection sensitivity of <= ‑42.5 dBZe at
1 kilometers.
4 The Radar Next system shall mitigate any detection gradients that occur within the blind range prior to dissemination from the radar sensor to the NWS, in cases where multiple pulses are used to achieve required range requirements.
Environmental
Question to Industry: Given the Radar Next solution must operate in the environmental ranges specified below, how do you plan to ensure compliance with these environmental requirements?
1 The Radar Next system shall be capable of withstanding sustained winds of at least 63 meters per second (140 miles per hour).
2 The Radar Next system shall be capable of operating at altitudes up to 3,300 meters (10,000 feet).
3 The Radar Next system shall be capable of withstanding an ambient temperature from -40 degrees C to +50 degrees C under operating conditions outdoors without degradation of system performance.
4 The Radar Next system shall be capable of withstanding an ambient temperature from -62 degrees C to +60 degrees C under non-operating conditions outdoors without degradation of system performance.
5 The Radar Next system shall be capable of withstanding 15% to 95% relative humidity under operating conditions outdoors without degradation of system performance.
6 The Radar Next system shall be capable of withstanding 15% to 95% relative humidity under
Attachment 2: Preliminary Draft Radar Next C-Band Requirements
Requirement Additional Notes / Qualifiers non-operating conditions outdoors without degradation of system performance.
7 The Radar Next system shall be capable of operating in rainfall rates of 300 millimeters per hour with maximum wind speed of 18 meters per second (40 miles per hour) without damage.
8 The Radar Next system shall be capable of withstanding 235 kilograms per square meter of snow and ice loading.
9 The Radar Next system shall be capable of operating in a 5% salt-fog atmosphere in compliance with MIL-STD-810.
10 The Radar Next system shall withstand blowing fine sand and dust particles with wind speeds up to 18 meters per second, and particle concentration of
0.177 grams per cubic meter with particle sizes up to 150 micrometers in diameter.
11 The Radar Next system shall withstand ultraviolet solar radiation with wavelengths < 0.38 microns, with intensities <= 75.35 watts per square meter (7 watts per square foot), or < 7 % of the total solar spectrum.
12 The Radar Next system shall withstand visible solar radiation with wavelengths between 0.38 microns and 0.78 microns, with intensities of <= 538.20 watts per square meter (50 watts per square foot), or < 48% of the total solar spectrum.
13 The Radar Next system shall withstand infrared solar radiation with wavelengths > 0.78 microns, with intensities of <= 775.0 watts per square meter
(72 watts per square foot), or < 69% of the total solar spectrum.
14 The Radar Next system shall withstand exposure to fungus, compliant with Guideline 4 (Fungus-Inert
Materials) of MIL-HDBK-454.
15 The Radar Next system shall provide protection against lightning and other sources of transient voltage, compliant with IEEE C62, NFPA 780, and
Attachment 2: Preliminary Draft Radar Next C-Band Requirements
Requirement Additional Notes / Qualifiers
Motorola R56 standards for surge protection, lightning protection, and grounding, respectively.
Weather Forecasting and Analysis Requirements: Data
Latency
1 The Radar Next system shall receive data continuously at the NWS ingest point, with latency between the observation time to the availability at the NWS ingest point of < 10 seconds, and with an average latency of < 3 seconds in any given 30-day period. Required data shall include sequence numbers/heartbeats, and state that missing, delayed beyond threshold, corrupted, or incomplete base-product data counts as a data-delivery failure. Buffering/backfilling later should not count as meeting operational availability.
Information obtained from a transmitted pulse shall be delivered within 3 seconds. Latency will be tracked from the point of measurement to product generation to the ingest point, which must be <=3 seconds on average.
Pedestal Requirements
1 The Radar Next system pedestal shall be capable of continuous 360 degree motion (both clockwise and counter-clockwise) in azimuth, and -3 to +110 degree movement in elevation.
2 The Radar Next system pedestal shall have a pointing resolution <= 0.0439 degrees (158 arcseconds).
3 The Radar Next system pedestal shall have a pointing accuracy <= 0.15 degrees in both azimuth and elevation from any starting position and for any requested change in position.
4 The Radar Next system pedestal shall be capable of a minimum velocity of <= 0.05 degree per second in both azimuth and elevation axes.
5 The Radar Next system pedestal shall be capable of azimuth rotation rates of >= 36 degrees per second.
6 The Radar Next system pedestal shall be capable of an elevation velocity of >= 30 degrees per second.
Attachment 2: Preliminary Draft Radar Next C-Band Requirements
Requirement Additional Notes / Qualifiers
7 The Radar Next system shall allow user-defined
Volume Coverage Patterns (VCPs).
8 The The Radar Next system VCPs shall provide the capability to change the following parameter on a cut-by-cut basis: pulse repetition rates; azimuth rotation rates; elevation position; algorithm selections, e.g., SZ-2, batch mode, staggered PRT, and clutter filtering techniques; and data display thresholds, e.g., SNR and signal quality index.
9 For Radar-as-a-Service (RaaS) solutions, the volume coverage pattern shall produce volumes that provide lowest-level updates every 90 seconds.
10 For RaaS solutions, the volume coverage pattern shall produce volumes that provide complete volume updates <= 6 minutes.
Operations and Sustainment Requirements: Availability
1 Operational availability in the Radar Next system shall be defined as the delivery and availability of data for all 6 base products 24/7/365.
2 The Radar Next system operational availability shall be >= 95%, where operational availability = (total hours annually - hours spent doing preventative maintenance annually - hours spent doing corrective maintenance annually - administrative down time annually - logistics down time annually)
/ total hours annually, and where total hours annually is 8760.
3 The Radar Next system shall be capable of operating continuously and autonomously on a
24/7/365 basis.
4 The radar data for the 6 base products shall be transmitted to the NWS collection point continuously and autonomously 24/7/365.
Operations and Sustainment Requirements: Reliability
Attachment 2: Preliminary Draft Radar Next C-Band Requirements
Requirement Additional Notes / Qualifiers
1 The Radar Next system shall operate such that no single planned or unplanned radar system or data outage shall last more than 24 hours (CONUS) or 72 hours (OCONUS).
Note: This does not include damages incurred through an act of God.
2 The Radar Next system shall operate such that the system Mean Time Between Failure (MTBF) is >=
800 hours, where MTBF = total operating time / number of failures, and where a failure is defined as (a) a condition that results in the radar no longer generating data; (b) a loss of communication between the radar and the NWS; and/or (c) a degradation severe enough to render the data unusable.
3 The Radar Next system shall operate such that the
Mean Time to Repair is <= 3 hours.
4 The Radar Next system shall operate such that the
Maximum Time to Repair is <=10 hours 95% of the time.
Additional Questions for Vendors
1 Installing C-Band radars on top of a water tower has been considered. However, some initial research indicates that 24x7 operations over 20 years may stress the water tower. As a vendor, how would you address this concern?
2 Do you use a Uninterruptible Power Supply (UPS) solution to provide power conditioning to critical radar equipment? If so, how long will the system operate on UPS power?
3 How long does it take for your C-Band radar system to switch to backup power, and what is the typical behavior? For example, is the switchover seamless or does the user have to reset the system?
4 What standards do you follow for grounding and lightning protection? What additional effort would be required to meet NFPA 780 and Motorola R56
Attachment 2: Preliminary Draft Radar Next C-Band Requirements
Requirement Additional Notes / Qualifiers standards?
5 What environments is your radar system designed to operate in / what standards do they comply with?
6 How are maintenance and calibration for your radar system being performed to ensure accuracy?
Specifically, how are Z, ZDR, PhiDP/system phase, rhohv/noise bias, antenna pointing, antenna pattern, radome effects, receiver noise, and transmitter power calibrated and monitored? How often would results be reported to NWS?
7 What level of cross-pol isolation can you achieve?
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