1. Introduction#

1.1 Context#

BIOMASS is ESA’s 7th Earth Explorer mission. The purpose of the BIOMASS is to reduce the uncertainty in the worldwide spatial distribution and dynamics of forest biomass in order to improve current assessments and future projections of the global carbon cycle. This objective will be achieved by the implementation of a P-band SAR mission, providing global maps of forest biomass stocks, forest disturbance and growth.

The BIOMASS mission will also provide 3D views of forests through the “tomographic” phase and will also support additional science needs arising from the opportunity to explore the Earth for the first time with a P-band SAR system from space offering the possibility to “see” below the vegetated areas and in beneath bare soil or icy regions.

To achieve its challenging objectives, the BIOMASS mission requires a specific data processing strategy that combines different technologies at different processing level in order to generate the final Above Ground Biomass global map.

1.2 Scope of the document#

The purpose of this document is to provide the “L1 Processor Algorithms Theoretical Baseline Document (ATBD)” for the BIOMASS Processing Suite (BPS) project.

This document is organized as follows:

Section 2: Brief introduction about BPS and L1 Processor;
Section 3: Description of L1 Pre-Processing algorithms;
Section 4: Description of L1 Core Processing algorithms;
Section 5: Description of L1 Post-Processing algorithms;
Section 6: Description of ancillary functions and parameters;
Section 7: Description of configurable input parameters;
Section 8: List of open points.

1.3 Acronyms#

Acronyms

Acronym	Description
AD	Applicable Document
ADC	Analog-to-Digital Converter
APID	Application Process IDentifier
ANC	ANCillary
ARESYS	Advanced Remote Sensing and Systems
ASM	Average Signal Magnitude
ATBD	Algorithm Theoretical Baseline Document
AUX	Auxiliary
BAQ	Bit Adaptive Quantization
BPS	BIOMASS Processing Suite
CAL	Calibration
CCDB	Calibration and Characterisation Data Base
CDASP	Characterised Doublet Antenna Secondary Pattern
CFI	Customer Furnished Items
CRC	Cyclical Redundancy Checking
DEM	Digital Elevation Model
DFDL	Data Format Description Language
DGM	Detected Ground-range Multilooked
ECSS	European Cooperation for Space Standardization
EO-CFI	Earth Observation Custom Furnished Items
ESA	European Space Agency
GLS	Generalised Least Square
GPP	Ground Processor Prototype
GPS	Global Positioning System
HK	House Keeping
HKTM	House Keeping TeleMetry
ICAL	Internal Calibration
IERS	International Earth Rotation Service
INT	Interferometric Phase
IRF	Impulse Response Function
ISLR	Integrated Sidelobe Ratio
ISP	Instrument Source Packet
L0	Level-0 product
L1a	Level-1a product
L1b	Level-1b product
L1M	Level-1 Monitoring product
L1S	Level-1 Standard product
L1PP	Level 1 Processor Prototype
LUT	Look-Up Table
PARC	Polarimetric Active Radar Calibrator
PAS	Power Amplifier Subsystem
PCAT	Packet CATegory
PF	Processing Facility
PFD	Product Format Specification Document
PGP	Power Gain Product
PID	Process IDentifier
PSLR	Peak-to-Sidelobe Ratio
PTAR	Point Target Ambiguity Ratio
QC	Quality Check
RD	Reference Document
RFI	Radio-Frequency Interferences
RXO	RX-Only product
SAR	Synthetic Aperture Radar
SCR	Signal-to-Clutter Ratio
SCS	Single-look Complex Slant-range
SNR	Signal-to-Noise Ratio
SSPA	Solid State Power Amplifier
SWL	Sample Window Length
SWP	Sampling Window Position
TBD	To Be Defined
TBC	To Be Confirmed
TOM	Tomographic Phase
UTC	Coordinated Universal Time
XML	`eXtended` Markup Language

1.4 Symbols and Variables#

Acronyms

Acronym	Description
\(f_r\)	Range frequency
\(f_a\)	Azimuth frequency
\(\omega_r\)	Range wavenumber
\(k_r\)	Range wavenumber after Stolt interpolation
\(k_a\)	Azimuth (Doppler) wavenumber
\(\tau\)	Fast time (slant range)
\(t\)	Slow time (azimuth)
\(\tau_r\)	Chirp duration in seconds
\(N_r\)	Chirp duration in samples
\(B_r\)	Chirp bandwidth
\(B_a\)	Azimuth bandwidth
\(f_0\)	Carrier frequency
\(\omega_0\)	Wavenumber at carrier frequency
\(\lambda\)	The wavelength
\(f_s\)	Range sampling frequency
\(PRF\)	Pulse repetition frequency
\(K_r\)	Chirp rate
\(K_a\)	Doppler rate
\(f_{DC}\)	Doppler centroid
\(v_s,\ v_s^i\)	Satellite velocity in ECEF and inertial reference frame, respectively
\(v_e,v_e^i\)	Effective velocity in ECEF and inertial reference frame, respectively
\(v_{e0C}\)	Effective velocity at reference range
\(v_g\)	Ground velocity
\(r_0\)	Zero-Doppler closest approach distance
\(r\)	Slant-range vector
\(\beta\)	Squint angle
\(c_0\)	Speed of light in vacuum
\(\Omega\)	One-way Faraday rotation angle
\(S_{xx}\)	Scattering coefficient at transmit/receive polarization \(xx\)
\(\widehat{k}\)	Unit propagation vector of transmitted wave
\(\overrightarrow{B}\)	Earth’s magnetic field vector
\(TEC\)	Total Electron Content
\(h_{iono}\)	Ionospheric height (thin layer model)
\(\theta\)	Incidence angle
\(\theta_l\)	Off-nadir look angle
\(\varphi_{iono}\)	Ionospheric phase screen
\(t_0\)	Zero-Doppler position for a given target
\(\boldsymbol{q}\)	Quaternions of the attitude product
\(\overrightarrow{p_{LOS}},\ \overrightarrow{p_{LOS,PF}}\)	Antenna pointing vector in the ECEF coordinates and in the pointing reference frame.
\(R_e,R_p\)	Equatorial and polar radius of the reference ellipsoid, respectively.

1.5 Applicable documents#

Code	Document
`[AD1]`	SAR Data ICD, `BIO-ICD-ADSF-SY-1000563385`, Issue 5
`[AD2]`	Biomass Coordinate System Definition Document, BIO.TCN.ASU.SY.00012, Issue 6
`[AD3]`	Instrument Internal Calibration Description, `BIO-PL-ADSF-SY-1000144284`, Issue 7.0
`[AD4]`	Processing of ICAL Data (Technical Memorandum), `BIO-TN-ADSP-SY-1000468852`, Issue 2.0, Nov. 2018
`[AD5]`	Action 77355 – Use of Antenna Pattern and ICAL Data for Ground Processing, `BIO-TN-ADSP-SY-1000362485`, Airbus D&S, Issue 1, May 2018
`[AD6]`	Instrument Data Processing Guidelines for the GPP, `BIO-NO-ADSS-SY-1001405024`, Issue 04, Apr 2025

1.6 Reference documents#

Code	Document
`[RD1]`	BIOMASS Ground Processor Prototype: L1 Algorithm Theoretical Baseline Document, BIO-GPP-ATBD-GP06, Issue 2.2, July 2022
`[RD2]`	F. Li, D. Held, J. Curlander, and C. Wu, “Doppler Parameter Estimation for Spaceborne Synthetic Aperture Radars,” IEEE Transactions on Geoscience and Remote Sensing, Jan. 1985.
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`[RD4]`	C. V. Jakowatz, Jr. and D. E. Whal, “Eigenvector method for maximumlikelihood estimation of phase errors in synthetic-aperture radar imagery,” J. Opt. Soc. Amer. A, Opt. Image Sci., vol. 10, no. 12, pp. 2539–2546, Oct. 1993.
`[RD5]`	D. E.Wahl, P. Eichel, D. C. Ghiglia, and C. V. Jakowatz, Jr., “Phase gradient autofocus—A robust tool for high resolution SAR phase correction,” IEEE Trans. Aerosp. Electron. Syst., vol. 30, no. 3, pp. 827–835, Jul. 1994.
`[RD6]`	W. Ye, T. S. Yeo, and Z. Bao, “Weighted least-squares estimation of phase errors for SAR/ISAR autofocus,” IEEE Trans. Geosci. Remote Sens., vol. 37, no. 5, pp. 2487–2494, Sep. 1999.
`[RD7]`	J. R. Moreira, “A new method of aircraft motion error extraction from radar raw data for real time motion compensation,” IEEE Trans. Geosci.Remote Sens., vol. 28, no. 4, pp. 620–626, Jul. 1990.
`[RD8]`	K. Camara de Macedo, R. Scheiber, A. Moreira, “An Autofocus Approach for Residual Motion Errors With Application to Airborne Repeat-Pass SAR Interferometry,” IEEE Transactions on Geoscience and Remote Sensing, Oct. 2008.
`[RD9]`	W. G. Carrara, R. S. Goodman, and R. M. Majewski, Spotlight Synthetic Aperture Radar—Signal Processing Algorithms. Boston, MA: Artech House, 1995.
`[RD10]`	S. H. Bickel and R. T. H. Bates, “Effects of magnetoionic propagation on the polarization scattering matrix,” Proc. IEEE, vol. 53, no. 8, pp. 1089-1901, 1965
`[RD11]`	“Ground Processing Strategy for RFI Mitigation - BIOMASS Phase B1”, BM-SS-ARE-RP-0042, Issue 2, ARESYS S.r.l.
`[RD12]`	J. S. Kim, K. Papathanassiou, R. Scheiber and S. Quegan, “Correcting distortion of polarimetric SAR data induced by ionospheric scintillation,” IEEE Transactions on Geoscinence and Remote Sensing, No. vol. 12, pp. 2015
`[RD13]`	ENVISAT Ground Segment – ASAR Processing and Product Quality Requirements – Appendix A.1, PO-RS-ESA-GS-00245, Issue 3.3, July 1997.
`[RD14]`	S. N. Madsen, “Estimating the Doppler centroid of SAR data,” in IEEE Transactions on Aerospace and Electronic Systems, vol. 25, no. 2, pp. 134-140, March 1989.
`[RD15]`	R Stolt, “Migration by Fourier transform”, Geophysics, 43:23–48, 1978.
`[RD16]`	F. Rocca, “Synthetic aperture radar: A new application for wave equation techniques”, Stanford Exploration Project Report, SEP-56:167–189, 1987.
`[RD17]`	R. Bamler, “A comparison of range-Doppler and wave-number domain SAR focusing algorithms”, IEEE Transactions on Geoscience and Remote Sensing, 30(4):706–713, July 1992.
`[RD18]`	D. D’Aria, A. Monti Guarnieri, “High-resolution space borne SAR focusing by SVD-Stolt”, Geoscience and Remote Sensing Letters, IEEE, 4(4):639–643, Oct. 2007.
`[RD19]`	E. Meler, U. Frei, D. Nüesch, “Precise Terrain Corrected Geocoded Images. In: SAR Geocoding: Data and Systems,” (Scheier G. ed.), Herbert Wichmann Verlag GmbH, Karlstuhe, pp.173-186, 1993.
`[RD20]`	J. J. Mohr, S.N. Madsen, “Geometric Calibration of ERS Satellite SAR Images,” IEEE Transactions on Geoscience and Remote Sensing, 39 (4), pp. 842-850, 2001.
`[RD21]`	E. Sansosti, P. Berardino, M. Manunta, F. Serafino, G. Fornaro, “Geometrical SAR image registration,” IEEE Transactions on Geoscience and Remote Sensing, 44(10), pp.2861-2870, 2006.
`[RD22]`	On Range Compression Approaches for the BIOMASS GPP, BIO-GPP-DLR-TN01, October 2018, DLR
`[RD23]`	BIOMASS GPP - Analysis of Transponder Delay Impacts on Impulse Response Function, ARE-012361, September 2018, ARESYS
`[RD24]`	Earth Observation Mission CFI Software: General Software User Manual, Deimos Space S.L.U., Issue 4.15, April 2018
`[RD25]`	[`BPS_AUX_FMT`] BPS Auxiliary Product Format, I/R 2/1/1
`[RD26]`	[`BPS_L1_PFD`] BIOMASS L1a/b/c Products Format Specification, I/R 1/2/2
`[RD27]`	Antenna Pattern Computation, `BIO-TN-ADSP-SY-1000550571`, Issue 02
`[RD28]`	W. H. Press, S. A. Teukolsky, W. T. Vetterling, B. P. Flannery, “Numerical Recipes in C”, Cambridge University Press, Second Edition
`[RD29]`	`BPS_TN_IONO`, “BIOMASS Ionospheric Corrections Technical Note”, I/R 1/0
`[RD30]`	Karam, L.J., and J. H. McClellan. “Complex Chebyshev Approximation for FIR Filter Design.” IEEE Transactions on Circuits and Systems II: Analog and Digital Signal Processing 42, no. 3 (March 1995): 207–216
`[RD31]`	Gomba, G., Parizzi, A., De Zan, F., Eineder, M., & Bamler, R. (2015). Toward operational compensation of ionospheric effects in SAR interferograms: The split-spectrum method. IEEE Transactions on Geoscience and Remote Sensing, 54(3), 1446-1461.
`[RD32]`	Altadill, D., S. Magdaleno, J.M. Torta, and E. Blanch C, “Global Empirical Models of the Density Peak Height and of the Equivalent Scale Height for Quiet Conditions”, Adv. Space Res. 52, 1756-1769, 2013.
`[RD33]`	timduly4/pyglow
`[RD34]`	Rino, C. L., & Fremouw, E. J. (1977). The angle dependence of singly scattered wavefields. Journal of Atmospheric and Terrestrial Physics, 39(8), 859-868.
`[RD35]`	Fremouw, E. J., & Secan, J. A. (1984). Modeling and scientific application of scintillation results. Radio Science, 19(03), 687-694.
`[RD36]`	Welch, P. D. (1967), “The use of Fast Fourier Transform for the estimation of power spectra: A method based on time averaging over short, modified periodograms” (PDF), IEEE Transactions on Audio and Electroacoustics, AU-15 (2): 70–73
`[RD37]`	`BIO-UDB-ADSF-SY-1000695798`, Instrument RDB, Version 17
`[RD38]`	Alken, P., Thébault, E., Beggan, C. D., Amit, H., Aubert, J., Baerenzung, J., … & Zhou, B. (2021). International geomagnetic reference field: the thirteenth generation. Earth, Planets and Space, 73(1), 1-25
`[RD39]`	`BPS_SDD`, “BPS Software Design Document”, I/R 3/2/4
`[RD40]`	ETAD-DLR-DD-0008, S-1 ETAD ATBD, I/R 2/3