Amnt 25 - Technical QA for PRD Rev E.pdf

Updated March 12, 2026

Technical Q&A for NS1 NEON SMBA PRD

NS1-SMBA-REQ-0001 Rev E

Below are questions and answers related to the Sounder for Microwave-Based Applications (SMBA) Performance Requirements Document (PRD), Revision E. In the event of any discrepancy, the final Request for Proposal provisions and contract terms will take precedence.

Question: How is the 𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁 calculated for heritage and non-heritage channels? How is the 𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁1/𝑓𝑓 calculated?

Answer: Microwave radiometer total noise 𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁 is commonly dominated by thermal noise 𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑡𝑡ℎ𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒 and 1/f noise 𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁1/𝑓𝑓 and may be calculated by:

SMBA PRD Equation 5: 𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁 = �(𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑡𝑡ℎ𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒)2 + (𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁1/𝑓𝑓)2�1/2

The thermal noise, 𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑡𝑡ℎ𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒, can be calculated by:

𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑡𝑡ℎ𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒 = 𝑇𝑇ℎ𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒 𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁 𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶 𝑡𝑡𝑡𝑡 𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁

√𝐵𝐵×𝜏𝜏

Where the “Thermal Noise Contribution to 𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁” is the value in the 4th column of Table 4.1-4, B is the channel bandwidth (the sum of all passbands in the channel) in MHz, and 𝜏𝜏 is the integration time in ms.

𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑡𝑡ℎ𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒 is then scaled for the SMBA design and sets the 𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑡𝑡ℎ𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒 limit.

For heritage channels, the channel bandwidth and the 𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁 requirements are listed in Table 4.1-3 and the integration time is established by the SMBA proposer’s design.

For non-heritage channels, integration time and channel bandwidth is established by the SMBA proposer’s design and the resulting 𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁 is reported in CDRL documentation.

For 𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁1/𝑓𝑓, SMBA-30 applies to both heritage and non-heritage channels.

The 1/f noise ratio, 𝑅𝑅1/𝑓𝑓 , can be calculated from

SMBA PRD Equation 6: 𝑅𝑅1/𝑓𝑓 = (𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁1/𝑓𝑓)2

𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁2

Example 1: Thermal Noise Contribution to 𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁 = 21.6𝐾𝐾 taken from Table 4.1-4 for V-band < 56 GHz, 𝐵𝐵 = 180 𝑀𝑀𝑀𝑀𝑀𝑀, and using 𝜏𝜏 = 18 𝑚𝑚𝑚𝑚 as an example, from the 𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑡𝑡ℎ𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒equation above, the resulting 𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑡𝑡ℎ𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒 = 0.3795𝐾𝐾.

Example 2: From Example 1, using 𝑅𝑅1/𝑓𝑓 = 0.1 as the max allowed by SMBA-30, with 𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁 = 0.4 K from Table 4.1-3, SMBA PRD Equation 6 can be used to solve for 𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁1/𝑓𝑓.

𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁1/𝑓𝑓 = �𝑅𝑅1/𝑓𝑓 × 𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁 = 0.1265𝐾𝐾

Example 3: Using the results from Examples 1 & 2, the 𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁 can now be computed using SMBA PRD Equation 5.

𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁 = �(𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑡𝑡ℎ𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒)2 + (𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁1/𝑓𝑓)2�1/2 = [(0.3795)2 + (0.1265)2]1/2 = 0.4𝐾𝐾

Question: Does the spatial horizontal resolution requirement (SMBA-44) apply to instantaneous footprint or aggregated footprint?

Answer: The spatial horizontal resolution requirement (SMBA-44) applies at an instant of time (i.e., Instantaneous Field of View) rather than over the time duration of a footprint.

IFOV is the portion of the Earth’s surface enclosed by the projected -3dB antenna contour at an instant of time (i.e., instantaneous footprint). An IFOV does not include smearing due to scanning or satellite orbital movement, nor any aggregating or spatial resampling of different footprints.

SMBA follows traditional practice of using the IFOV to check compliance with requirements for imaging without spatial gaps in the along-scan or along-track directions. The SMBA footprint size requirements (SMBA-42 and SMBA-44) must be met at the IFOV level at nadir.

Question: Is compliance to the new passband gain ripple requirement (SMBA-41) constrained to front end hardware design?

Answer: SMBA-41 is agnostic of hardware design and/or software design choices employed to comply.

Question: Will the SMBA instrument be powered ON or OFF during launch?

Answer: PRD is written to be inclusive of instrument designs that require being powered ON and instrument designs that require being OFF at launch.