Traceable Radiometry Underpinning Terrestrial and Helio Studies

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%)".

The cryogenic radiometer is the primary standard used by national metrology institutes for radiometric measurements and "recommended as the means to achieve SI traceability".{{Cite web |title=TRUTHS (Traceable Radiometry Underpinning Terrestrial-and Helio-Studies) - eoPortal |url=https://www.eoportal.org/satellite-missions/truths#mission-data-products-and-performance-requirements |access-date=2023-12-05 |website=www.eoportal.org |language=en}} The CSAR, which would be cooled to <60 K, is therefore considered "the heart of the calibration system". The mission would be the first to host a primary standard cryogenic radiometer aboard a satellite. 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. The HIS can then be used to image the Earth, the Moon, and also to "measure incident solar spectral irradiance."

The mission is led by the UK National Physical Laboratory (NPL) and its lead scientist for EO, Nigel Fox.{{Cite web |title=Nigel Fox |url=https://www.npl.co.uk/people/nigel-fox |access-date=2024-01-12 |website=NPLWebsite |language=en}} It has two primary objectives:{{Cite web |title=Mission objectives |url=https://www.npl.co.uk/earth-observation/truths/missions-goals |access-date=2023-12-03 |website=National Physical Laboratory |language=en}}{{Quotebox

| width = 70%

| align = left|"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."

}}{{clear}}

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

File:TRUTHS mission patch.png]]

{{External video

|video1=[https://www.youtube.com/watch?v=ee7tAjTHm4M TRUTHS mission explanation] - Space4Climate (2021){{Cite web |date=2020-02-26 |title=TRUTHS |publisher=Space4Climate |url=https://space4climate.com/truths/ |access-date=2023-12-02 |language=en-GB}}

|video2=[https://www.youtube.com/watch?v=-_BznE1Ckgc Onboard Calibration System (OBCS) animation] - National Physical Laboratory (2019){{Cite web |title=SI traceability in-flight |url=https://www.npl.co.uk/earth-observation/truths/satellite-calibration |access-date=2023-12-02 |publisher=National Physical Laboratory |language=en}}}}

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.{{Cite journal |last1=Fox |first1=Nigel P. |last2=Aiken |first2=James |last3=Barnett |first3=John J. |last4=Briottet |first4=Xavier |last5=Carvell |first5=Ray |last6=Froehlich |first6=Claus |last7=Groom |first7=Steven B. |last8=Hagolle |first8=Olivier |last9=Haigh |first9=Joanna D. |last10=Kieffer |first10=Hugh H. |last11=Lean |first11=Judith |last12=Pollock |first12=David B. |last13=Quinn |first13=Terence John |last14=Sandford |first14=Michael C. W. |last15=Schaepman |first15=Michael E. |editor-first1=Hiroyuki |editor-first2=Joan B. |editor-first3=Michelle L. |editor-first4=Konradin |editor-last1=Fujisada |editor-last2=Lurie |editor-last3=Aten |editor-last4=Weber |date=2003-04-08 |title=Traceable radiometry underpinning terrestrial- and helio-studies (TRUTHS) |url=https://www.spiedigitallibrary.org/conference-proceedings-of-spie/4881/0000/Traceable-radiometry-underpinning-terrestrial--and-helio-studies-TRUTHS/10.1117/12.462438.full |journal=Sensors, Systems, and Next-Generation Satellites VI |publisher=SPIE |volume=4881 |pages=395–406 |doi=10.1117/12.462438 |bibcode=2003SPIE.4881..395F |display-authors=2|url-access=subscription }}{{Cite book |last1=Fox |first1=Nigel |last2=Green |first2=Paul |last3=Winkler |first3=Rainer |last4=Lobb |first4=Daniel |last5=Friend |first5=Jonathan |title=2016 IEEE International Geoscience and Remote Sensing Symposium (IGARSS) |display-authors=2 |chapter=Traceable Radiometery Underpinning Terrestrial- and Helio- Studies (TRUTHS): Establishing a climate and calibration observatory in space |date=2016 |pages=1939–1942 |chapter-url=https://ieeexplore.ieee.org/document/7729499 |access-date=2023-12-03 |doi=10.1109/igarss.2016.7729499|isbn=978-1-5090-3332-4 }}{{Cite report |url=http://eprintspublications.npl.co.uk/id/eprint/9319 |title=SI-traceable space-based climate observation system: a CEOS and GSICS Workshop. National Physical Laboratory, UK, 9-11 Sept 2019 |last1=Boesch |first1=H |last2=Brindley |first2=H |date=2022-01-25 |publisher=National Physical Laboratory |doi=10.47120/npl.9319 |last3=Carminati |first3=F |last4=Fox |first4=N |last5=Helder |first5=D |last6=Hewison |first6=T |last7=Houtz |first7=D |last8=Hunt |first8=S |last9=Kopp |first9=G |display-authors=2}}{{Cite journal |last1=Fox |first1=Nigel |last2=Green |first2=Paul |date=2020-07-27 |title=Traceable Radiometry Underpinning Terrestrial- and Helio-Studies (TRUTHS): An Element of a Space-Based Climate and Calibration Observatory |journal=Remote Sensing |language=en |volume=12 |issue=15 |pages=2400 |doi=10.3390/rs12152400 |doi-access=free |bibcode=2020RemS...12.2400F |issn=2072-4292}}{{Cite journal |last1=Fox |first1=Nigel |last2=Kaiser-Weiss |first2=Andrea |last3=Schmutz |first3=Werner |last4=Thome |first4=Kurtis |last5=Young |first5=Dave |last6=Wielicki |first6=Bruce |last7=Winkler |first7=Rainer |last8=Woolliams |first8=Emma |date=2011-10-28 |title=Accurate radiometry from space: an essential tool for climate studies |url=https://royalsocietypublishing.org/doi/10.1098/rsta.2011.0246 |journal=Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences |language=en |volume=369 |issue=1953 |pages=4028–4063 |doi=10.1098/rsta.2011.0246 |pmid=21930564 |bibcode=2011RSPTA.369.4028F |issn=1364-503X |display-authors=2|url-access=subscription }}{{Cite report |url=https://meetingorganizer.copernicus.org/EGU23/EGU23-12399.html |title=Traceable Radiometry Underpinning Terrestrial- and Helio- Studies (TRUTHS) – A 'gold standard' imaging spectrometer in space to support climate emergency reseaerch |last1=Fehr |first1=Thorsten |last2=Fox |first2=Nigel |date=2023-02-22 |publisher=Copernicus Meetings |issue=EGU23-12399 |doi=10.5194/egusphere-egu23-12399 |language=en |last3=Marini |first3=Andrea |last4=Remedios |first4=John |doi-access=free |display-authors=2|url-access=subscription }}

Timeline:{{Cite web |date=July 2023 |title=TRUTHS Mission Explainer |url=https://space4climate.com/wp-content/uploads/TRUTHS-Mission-Explainer-July-2023.pdf |website=space4climate.com |publisher=Space4Climate}}

• Early 2000s – Mission proposed by the UK National Physical Laboratory (NPL)
• 2019 – Adopted at the ESA ministerial conference, with 85% funding from the UK. The remainder from Switzerland, Greece, Czechia, and Romania.{{Cite news |date=2020-01-22 |title=Space mission to reveal 'Truths' about climate change |language=en-GB |work=BBC News |url=https://www.bbc.com/news/science-environment-51197453 |access-date=2023-12-03}}{{Cite web |last=Norman |first=Helen |date=2020-02-03 |title=Europeans discuss TRUTHS climate change mission |url=https://www.meteorologicaltechnologyinternational.com/news/satellites/europeans-discuss-truths-climate-change-mission.html |access-date=2023-12-03 |website=Meteorological Technology International |language=en-GB}}
• 2020 – Airbus UK selected as lead contractor,{{Cite web |title=Airbus wins European Space Agency TRUTHS mission study for metrological traceability of Earth observation data |url=https://www.airbus.com/en/newsroom/press-releases/2020-11-airbus-wins-european-space-agency-truths-mission-study-for |access-date=2023-12-03 |website=www.airbus.com|date=28 October 2021 }} Teledyne e2v selected to provide the infrared detectors.{{Cite web |last= |date=2020-12-02 |title=Teledyne e2v to supply Infrared detector for TRUTHS Climate Change Satellite |url=https://www.ukspace.org/teledyne-e2v-to-supply-infrared-detector-for-truths-climate-change-satellite/ |access-date=2023-12-03 |website=UKspace |language=en-GB}}
• 2021 – At COP26: Began early design phase.{{Cite web |last=Jewett |first=Rachel |date=2021-11-05 |title=UK-Led TRUTH Mission to Fight Climate Change Moves to Early Design Phase |url=https://www.satellitetoday.com/imagery-and-sensing/2021/11/05/uk-led-truth-mission-to-fight-climate-change-moves-to-early-design-phase/ |access-date=2023-12-03 |website=Via Satellite |language=en}}
• 2022 – Passed preliminary design, technical, and scientific reviews.{{Cite web |date=2022-10-12 |title=The TRUTHS climate satellite mission passes key test - Space4Climate |url=https://space4climate.com/the-truths-climate-satellite-mission-passes-key-test/ |access-date=2023-12-03 |language=en-GB}} Received further funding at the ESA ministerial conference.{{Cite web |title=NPL TRUTHS mission receives funding |url=https://www.npl.co.uk/news/npl-truths-mission-receives-funding |access-date=2023-12-03 |website=NPLWebsite |language=en}}
• 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.{{Cite web |title=COP28: UK climate satellite contracts |url=https://www.gov.uk/government/news/cop28-uk-climate-satellite-contracts |access-date=2023-12-05 |website=GOV.UK |language=en}}
• ~ 2030 – Estimated launch, aboard a Vega-C from the Guiana Space Centre.

The mission would have a targeted duration of eight or more years, and a minimum duration of five.

• CLARREO

• [https://www.npl.co.uk/earth-observation/truths/ National Physical Laboratory]
• [https://space4climate.com/truths/ Space4climate]
• [https://www.esa.int/Applications/Observing_the_Earth/TRUTHS European Space Agency]
• [https://ceoi.ac.uk/technologies/optical-spectroscopy/truths/ Centre for EO instrumentation]
• [https://www.eoportal.org/satellite-missions/truths EOportal] ([https://database.eohandbook.com/database/missionsummary.aspx?missionID=982 Mission ID 982])
• [https://space.oscar.wmo.int/satelliteprogrammes/view/truths World Meteorological Organisation OSCAR database] ([https://space.oscar.wmo.int/instruments/view/csar CSAR], [https://space.oscar.wmo.int/instruments/view/his HIS])

Category:2030s in spaceflight

Category:Atmospheric radiation

Category:Earth observation satellites

Category:National Physical Laboratory (United Kingdom)