Atomic Clock Ensemble in Space
{{Short description|Experiment}}
File:SpaceX CRS-32 Launch 1.jpg rocket with the CRS-32 Cargo Dragon capsule carying ACES to the International Space Station]]
The Atomic Clock Ensemble in Space (ACES) is a project led by the European Space Agency (ESA), placing ultra-stable atomic clocks on the International Space Station (ISS). It was launched{{Cite web |title=ACES on its way to space |url=https://www.esa.int/ESA_Multimedia/Images/2025/04/ACES_on_its_way_to_space |access-date=2025-04-22 |website=www.esa.int |language=en}} and installed on the Columbus External Payload Facility in April 2025.{{Cite web |title=ACES finds its home in orbit |url=https://www.esa.int/Science_Exploration/Human_and_Robotic_Exploration/ACES_finds_its_home_in_orbit |access-date=2025-04-25 |website=www.esa.int |language=en}} Operation in the microgravity environment of the ISS provides a stable and accurate time base for different areas of research, including general relativity and string theory tests, time and frequency metrology, and very long baseline interferometry.
Instruments
The payload contains two clocks: a caesium laser cooled atomic clock (PHARAO) developed by CNES, France for long-term stability and an active hydrogen maser (SHM) developed by Spectratime, Switzerland for short-term stability.{{cite web|url=http://www.spectratime.com/uploads/documents/ispace/ESA_CAS_Legacy_Appln.pdf|title=Swiss Space Atomic Clock Technologies and Applications in Space Science|publisher=SpectraTime|date=|accessdate=11 February 2017|archive-url=https://web.archive.org/web/20170212090948/http://www.spectratime.com/uploads/documents/ispace/ESA_CAS_Legacy_Appln.pdf|archive-date=12 February 2017|url-status=dead}}{{cite web
|author=ESA
|author-link=ESA
|date=
|title= Atomic clock ensemble in space (ACES)
|url=http://wsn.spaceflight.esa.int/docs/Factsheets/20%20ACES%20LR.pdf
|work=ERASMUS Centre - Directorate of Human Spaceflight and Operations
|doi=
|accessdate=11 February 2017
}} The onboard frequency comparison between PHARAO and SHM will be a key element for the evaluation of the accuracy and the short/medium-term stability of the PHARAO clock, it will allow the identification of the optimal operating conditions for PHARAO and to select a compromise between frequency accuracy and stability.{{cite web|url=http://www.spectratime.com/uploads/documents/ispace/ESA_CAS_Legacy_Appln.pdf|title=Swiss Space Atomic Clock Technologies and Applications in Space Science|publisher=SpectraTime|date=|accessdate=11 February 2017|archive-url=https://web.archive.org/web/20170212090948/http://www.spectratime.com/uploads/documents/ispace/ESA_CAS_Legacy_Appln.pdf|archive-date=12 February 2017|url-status=dead}}{{cite web
|author=ESA
|author-link=ESA
|date=25 July 2014
|title= Timely Arrival of PHARAO Space Clock
|url=http://www.esa.int/Our_Activities/Human_Spaceflight/Research/Timely_arrival_of_Pharao_space_clock
|work=ESA
|doi=
|accessdate=11 February 2017
}} The mission will also be a test-bed for the space qualification of the active hydrogen maser SHM. Afterwards, optimisation performances in the {{nowrap|2 × 10−16}} range for both frequency instability and inaccuracy are intended, this corresponds to a time error of about 1 second over 300 million ({{nowrap|300 × 106}}) years.
Timeline
- After earlier plans for launch readiness in 2012,{{cite journal |title=Space clocks and fundamental tests: The ACES experiment |date=2009 |url=https://link.springer.com/article/10.1140/epjst/e2009-01041-7 |publisher=THE EUROPEAN PHYSICAL JOURNAL |doi=10.1140/epjst/e2009-01041-7 |accessdate=9 March 2023 |last1=Cacciapuoti |first1=L. |last2=Salomon |first2=Ch. |journal=The European Physical Journal Special Topics |volume=172 |issue=1 |pages=57–68 |bibcode=2009EPJST.172...57C |s2cid=119402539 |url-access=subscription }} the clock ensemble was expected to travel to the space station aboard a Falcon 9 in 2021.{{cite web |title=PHARAO |date=24 April 2015 |url=https://pharao.cnes.fr/en/PHARAO/index.htm |publisher=Centre national d’études spatiales(CNES) |accessdate=2 August 2020}} Major delays due to difficulties in the development and testing of the active hydrogen maser and the time transfer microwave system extended the launch to 2025{{cite web |title=ACES Workshop 2022 |url=https://aces2022.sciencesconf.org/ |publisher=CCSD |accessdate=8 March 2023}}
- ACES was launched to the ISS on 21 April 2025 on a SpaceX Falcon 9 rocket
- On April 25, 2025, ACES was installed on the Earth-facing side of ESA’s Columbus laboratory module using the Canadian robotic arm. A six-month commissioning phase will follow{{Cite web |title=ACES: Atomic Clock Ensemble in Space |url=https://www.esa.int/Science_Exploration/Human_and_Robotic_Exploration/ACES_Atomic_Clock_Ensemble_in_Space |access-date=2025-04-26 |website=www.esa.int |language=en}}
- The first activation of ACES, which will establish communications with ground control and stabilise thermal systems, is scheduled for 28 April
- ESA expects a 30-month operations phase for ACES{{cite web|url=https://pharao.cnes.fr/en/PHARAO/GP_platform_aces.htm|title=ACES Platform|date=8 September 2014|publisher=ESA|accessdate=31 January 2016}}
See also
References
{{Reflist}}
External links
- [http://wsn.spaceflight.esa.int/docs/others/aces_flyer.pdf ACES factsheet by the ESA (PDF)]
{{DEFAULTSORT:Atomic Clock Ensemble In Space}}
Category:International Space Station experiments
Category:Columbus (ISS module)
Category:European Space Agency
{{Europe-spacecraft-stub}}