TRACE

Transition Region and Coronal Explorer (TRACE) was a NASA heliophysics and solar observatory designed to investigate the connections between fine-scale magnetic fields and the associated plasma structures on the Sun by providing high resolution images and observation of the solar photosphere, the transition region, and the corona. A main focus of the TRACE instrument is the fine structure of coronal loops low in the solar atmosphere. TRACE is the fourth spacecraft in the Small Explorer program, launched on April 2, 1998, and obtained its last science image on 21 June 2010 23:56 UT.[6]

Transition Region and Coronal Explorer
Illustration of TRACE
NamesExplorer-73, SMEX-4
Mission typeHeliophysics
OperatorNASA / GSFC
COSPAR ID1998-020A
SATCAT no.25280
Websitetrace.lmsal.com
Mission durationPlanned: 1 year
Final: 12 years, 2 months and 19 days[1]
Spacecraft properties
ManufacturerNASA / GSFC
Lockheed Martin[2]
Launch mass250 kg (551 lb)[2]
Dimensions1.9 × 1.1 m (6.2 × 3.6 ft)[2]
Power220 W[3]
Start of mission
Launch dateApril 2, 1998, 02:43:23 (1998-04-02UTC02:43:23Z) UTC[4]
RocketPegasus XL
Launch siteStargazer, Vandenberg AFB
ContractorOrbital Sciences
Entered serviceApril 20, 1998[2]
End of mission
DisposalDecommissioned
Deactivated21 June 2010
Orbital parameters
Reference systemGeocentric
RegimeSun synchronous
Semi-major axis6,914.2 km (4,296.3 mi)
Eccentricity0.00267
Perigee altitude517.6 km (321.6 mi)
Apogee altitude554.5 km (344.6 mi)
Inclination97.5325°
Period95.3667 min
RAAN89.297°
Argument of perigee91.5219°
Mean anomaly32.1161°
Mean motion15.1 rev/day
EpochSeptember 10, 2015, 19:19:29[5]
Revolution no.95290
Main telescope
NameTRACE Imaging Telescope
TypeCassegrain[2]
Diameter30 cm (12 in)[2]
Focal length8.66 m (28.4 ft)[2]
WavelengthsUltraviolet and extreme ultraviolet[2]
Resolution1 arcsec[2]
Small Explorer program
 

The satellite was built by NASA's Goddard Space Flight Center. Its telescope was constructed by a consortium led by Lockheed Martin's Advanced Technology Center. The optics were designed and built to a state-of-the-art surface finish by the Smithsonian Astrophysical Observatory (SAO). The telescope has a 30 cm (12 in) aperture and 1024×1024 CCD detector giving an 8.5 arc minute field of view. The telescope is designed to take correlated images in a range of wavelengths from visible light through the Lyman alpha line to far ultraviolet. The different wavelength passbands correspond to plasma emission temperatures from 4,000 to 4,000,000 K. The optics use a special multilayer technique to focus the difficult-to-reflect EUV light; the technique was first used for solar imaging in the late 1980s and 1990s, notably by the MSSTA and NIXT sounding rocket payloads.

  • TRACE image of some typical million Kelvin loops
  • Image of a sunspot taken by TRACE
  • TRACE mosaic of the full-disk Sun

References
  1. "TRACE science mission terminated". Lockheed Martin Solar and Astrophysics Lab. June 21, 2010. Retrieved September 13, 2015.
  2. Rumerman, Judy A. (2009). NASA Historical Data Book, Volume VII: NASA Launch Systems, Space Transportation/Human Spaceflight, and Space Science 1989-1998 (PDF). NASA History Series. NASA. pp. 812–813. ISBN 978-0-16-080501-1. SP-2009-4012.
  3. "TRACE". National Space Science Data Center. NASA. Retrieved September 13, 2015.
  4. "TRACE - Trajectory Details". National Space Science Data Center. NASA. Retrieved September 13, 2015.
  5. "TRACE - Orbit". Heavens Above. September 10, 2015. Retrieved September 10, 2015.
  6. "Transition Region and Coronal Explorer". Lockheed Martin Solar and Astrophysics Lab.

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