Traceable Radiometry Underpinning Terrestrial and Helio Studies

This article is about a satellite mission. For other uses, see Truth (disambiguation).

TRUTHS

TRUTHS mission patch
Names	Traceable Radiometry Underpinning Terrestrial- and Helio-Studies
Mission type	Solar radiation measurement, traceability
Mission duration	5-8+ years (planned)
Start of mission
Launch date	~2030
Rocket	Vega-C (planned)
Launch site	Centre Spatial Guyanais
Orbital parameters
Reference system	Geocentric
Regime	Polar
Altitude	610 km
Inclination	90°
Period	96.9 minutes [1]
Repeat interval	61 days
Instruments
CSAR - cryogenic solar absolute radiometer HIS - hyperspectral imaging spectrometer

TRUTHS(Traceable Radiometry Underpinning Terrestrial- and Helio-Studies) is a planned European Space Agency (ESA) satellite. It is meant to improve the accuracy, reliability, and integrity of Earth observation data, ^[2] and to be the first of a new class of "SI-traceable satellites" (SITSats) that will enable other Earth observation missions to calibrate measurements with reference to them. ^[3] The mission is led by the UK National Physical Laboratory (NPL) and its lead scientist for Earth observation, Nigel Fox. ^[4]

Science goals

It has two primary objectives: ^[5]

• "Climate benchmarking through high-accuracy direct hyperspectral measurements of the Earth’s incoming and outgoing radiation to enhance our ability to estimate the Earth’s radiation budget by an order of magnitude, enabling detection of climate signals in the shortest possible time."

• "To establish a gold-standard reference dataset against which to cross-calibrate other sensors, facilitating an upgrade to the performance of the global Earth observing system to ensure interoperability and robust anchoring to an SI reference in space."

A secondary objective of the mission is the use the global hyperspectral data to "constrain and improve retrieval algorithms". ^[6]

Science instruments

Alongside communications and navigation equipment, the scientific payload of the satellite would include three instruments: the cryogenic solar absolute radiometer (CSAR), the onboard calibration system (OBCS), and the hyperspectral imaging spectrometer (HIS).

The instruments would produce global hyperspectral (320 nm to 2400 nm) measurements of "top-of-atmosphere earth spectral radiance (0.3% k=2); solar irradiance (both total and spectrally resolved, 0.02% and 0.3% respectively); and lunar spectral irradiance (0.3%)". ^[3]

The cryogenic radiometer is the primary standard used by national metrology institutes for radiometric measurements and "recommended as the means to achieve SI traceability". ^[6] The CSAR, which would be cooled to < 60 K, is therefore considered "the heart of the calibration system". ^[6]

The mission would be the first to host a primary standard cryogenic radiometer aboard a satellite. ^[3] The OBCS would "...transfer calibration traceability from the SI defining power measurement... to a full spectrally resolved radiance calibration of an instrument" – in the case of TRUTHS from the CSAR to the HIS – in a simplified manner to the steps used by terrestrial metrology institutes. ^[6] The HIS can then be used to image the Earth, the Moon, and also to "measure incident solar spectral irradiance." ^[6]

Timeline

• In order to obtain both scientific and financial support for the mission, many reports and academic publications were produced by Fox and collaborators over several decades. ^{[7] [8] [9] [10] [11] [12]}

• Early 2000s – Mission proposed by the UK National Physical Laboratory (NPL) ^[13]
• 2019 – Adopted at the ESA ministerial conference, with 85% funding from the UK. The remainder from Switzerland, Greece, Czechia, and Romania. ^{[14] [15]}
• 2020 – Airbus UK selected as lead contractor, ^[16] Teledyne e2v selected to provide the infrared detectors. ^[17]
• 2021 – At COP26: Began early design phase. ^[18]
• 2022 – Passed preliminary design, technical, and scientific reviews. ^[19] Received further funding at the ESA ministerial conference. ^[20]
• 2023 – Further funding awarded during COP28, to Airbus UK for design and development; and to Teledyne e2v to construct the hyperspectral imaging spectrometer detection system. ^[21]
• ~ 2030 – Estimated launch, aboard a Vega-C from the Guiana Space Centre. ^[13]

• The mission would have a targeted duration of eight or more years, and a minimum duration of five. ^[6]

See also

• List of European Space Agency programmes and missions
• CLARREO

References

1. "THE CEOS DATABASE : MISSION, INSTRUMENTS AND MEASUREMENTS - TRUTHS". database.eohandbook.com. Retrieved 2023-12-05.
2. "Mission objectives". NPLWebsite. Retrieved 2023-12-05.
3. "Learn more about TRUTHS". NPLWebsite. Retrieved 2023-12-05.
4. "Nigel Fox". NPLWebsite. Retrieved 2024-01-12.
5. "Mission objectives". National Physical Laboratory. Retrieved 2023-12-03.
6. "TRUTHS (Traceable Radiometry Underpinning Terrestrial-and Helio-Studies) - eoPortal". www.eoportal.org. Retrieved 2023-12-05.
7. Fox, Nigel P.; Aiken, James; et al. (2003-04-08). Fujisada, Hiroyuki; Lurie, Joan B.; Aten, Michelle L.; Weber, Konradin (eds.). "Traceable radiometry underpinning terrestrial- and helio-studies (TRUTHS)" . Sensors, Systems, and Next-Generation Satellites VI. 4881. SPIE: 395–406. Bibcode:2003SPIE.4881..395F. doi:10.1117/12.462438.
8. Fox, Nigel; Green, Paul; et al. (2016). "Traceable Radiometery Underpinning Terrestrial- and Helio- Studies (TRUTHS): Establishing a climate and calibration observatory in space". 2016 IEEE International Geoscience and Remote Sensing Symposium (IGARSS). pp. 1939–1942. doi:10.1109/igarss.2016.7729499. ISBN   978-1-5090-3332-4.
9. Boesch, H; Brindley, H; et al. (2022-01-25). SI-traceable space-based climate observation system: a CEOS and GSICS Workshop. National Physical Laboratory, UK, 9-11 Sept 2019 (Report). National Physical Laboratory. doi:10.47120/npl.9319.
10. Fox, Nigel; Green, Paul (2020-07-27). "Traceable Radiometry Underpinning Terrestrial- and Helio-Studies (TRUTHS): An Element of a Space-Based Climate and Calibration Observatory". Remote Sensing. 12 (15): 2400. Bibcode:2020RemS...12.2400F. doi: 10.3390/rs12152400 . ISSN   2072-4292.
11. Fox, Nigel; Kaiser-Weiss, Andrea; et al. (2011-10-28). "Accurate radiometry from space: an essential tool for climate studies" . Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences. 369 (1953): 4028–4063. Bibcode:2011RSPTA.369.4028F. doi:10.1098/rsta.2011.0246. ISSN   1364-503X. PMID   21930564.
12. Fehr, Thorsten; Fox, Nigel; et al. (2023-02-22). Traceable Radiometry Underpinning Terrestrial- and Helio- Studies (TRUTHS) – A 'gold standard' imaging spectrometer in space to support climate emergency reseaerch (Report). Copernicus Meetings. doi: 10.5194/egusphere-egu23-12399 .
13. "TRUTHS Mission Explainer" (PDF). space4climate.com. Space4Climate. July 2023.
14. "Space mission to reveal 'Truths' about climate change". BBC News. 2020-01-22. Retrieved 2023-12-03.
15. Norman, Helen (2020-02-03). "Europeans discuss TRUTHS climate change mission". Meteorological Technology International. Retrieved 2023-12-03.
16. "Airbus wins European Space Agency TRUTHS mission study for metrological traceability of Earth observation data". www.airbus.com. 28 October 2021. Retrieved 2023-12-03.
17. "Teledyne e2v to supply Infrared detector for TRUTHS Climate Change Satellite". UKspace. 2020-12-02. Retrieved 2023-12-03.
18. Jewett, Rachel (2021-11-05). "UK-Led TRUTH Mission to Fight Climate Change Moves to Early Design Phase". Via Satellite. Retrieved 2023-12-03.
19. "The TRUTHS climate satellite mission passes key test - Space4Climate". 2022-10-12. Retrieved 2023-12-03.
20. "NPL TRUTHS mission receives funding". NPLWebsite. Retrieved 2023-12-03.
21. "COP28: UK climate satellite contracts". GOV.UK. Retrieved 2023-12-05.

External links

External videos
TRUTHS mission explanation - Space4Climate (2021) [1]
Onboard Calibration System (OBCS) animation - National Physical Laboratory (2019) [2]

• National Physical Laboratory
• Space4climate
• European Space Agency
• Centre for EO instrumentation
• EOportal (Mission ID 982)
• World Meteorological Organisation OSCAR database (CSAR, HIS)

1. "TRUTHS". Space4Climate. 2020-02-26. Retrieved 2023-12-02.
2. "SI traceability in-flight". National Physical Laboratory . Retrieved 2023-12-02.