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USA 200



USA 200 is an American military (NRO) reconnaissance satellite that was launched by an Atlas 5 rocket from Vandenberg AFB at 10:02 UT on 13 March 2008.


USA 200 also carried the TWINS 2 (Two Wide-angle Imaging Neutral-atom Spectrometer) instrumentation, a mission of opportunity under NASA's Small Explorer (SMEX) program. Companion instrumentation (TWINS 1) was flown on-board the USA 184 (2006-027A) launch.

TWINS is a stereo mission whose overall scientific objective is to establish the global connectivities and causal relationships between processes in different regions of the Earth's magnetosphere. To meet this goal TWINS 1 and 2 provide stereoscopic neutral atom imaging of the magnetosphere from two widely-spaced, high-altitude, high-inclination spacecraft. TWINS instrumentation includes an energetic neutral atom (ENA) imager to capture charge-exchange-produced neutral atoms over a broad entergy range (approximately 1-100 keV) and a Lyman-alpha detector to measure the density of the neutral hydrogen geocorona needed to extract megnetospheric ion fluxes from neutral atom data. More information on the TWINS instrumentation can be found under experiment information.

The spacecraft carrying the TWINS instruments is three-axis stabilized and approximately nadir-pointing. TWINS operates only during the apogee portion of each orbit, when the spacecraft is above the radiation belts. Data is acquired with a time resolution of 60 s. However, the time required to change actuator direction between scans (no data collection) was 25 s from June 2008 to July 2009, and 12 s at all other times. This gives an effective cadence of 72 or 85 s. The nominal design lifetime for the instrumentation is four years.

Alternate Names

  • 32706
  • NROL 28
  • TWINS 2
  • TWINS2

Facts in Brief

Launch Date: 2008-03-13
Launch Vehicle: Atlas V
Launch Site: Vandenberg AFB, United States

Funding Agencies

  • National Reconnaissance Office (United States)
  • National Aeronautics and Space Administration (United States)
  • Department of Energy (United States)


  • Surveillance and Other Military
  • Space Physics

Additional Information

Questions and comments about this spacecraft can be directed to: Coordinated Request and User Support Office



NameRoleOriginal AffiliationE-mail
Dr. James R. SharberProgram ScientistNASA
Dr. David J. McComasMission Principal InvestigatorLos Alamos National
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