Landsat 8

Landsat 8 Maneuvers

In order to maintain a consistent equatorial crossing time, the Landsat spacecrafts must occasionally undergo maneuvers using the satellite's propulsion subsystem to fire thrusters and bring about a change in the orbital elements. 

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Maneuver definitions

December 21, 2017 (DOY355): At approximately 5:25 am CST (11:25 UTC) Thursday, December 21, 2​0​17, Landsat 8 operations will be suspended for a short period of time during an orbit correction maneuver. No data will be acquired during this maneuver. Normal operations are expected to resume by 9:25 am CST (15:25 UTC) on Thursday, December 21, 2017. The Landsat Flight Operations Team are performing this maneuver to arrest Landsat 8's westward drift across its WRS-2 ground track. The enhanced westward drift is a result of an emergency Risk Mitigation Maneuver (RMM) that was performed on Saturday, 9 December 2017, to avoid object Defense Meteorological Satellite Program Debris (#29068).

April 29-30, 2014 (Satellite in Safehold Condition): On April 29, 2014 (DOY 120) at 05:44:13 UTC (11:44 pm CT April 28, 2014 9DOY 119), the Landsat 8 satellite entered a ‘safehold’ condition that suspended all data acquisitions. Normal acquisitions resumed shortly after 23:00 UTC (5:00 pm CT) on April 30, 2014 (DOY 121).

September 19-21, 2013 (Satellite in Safehold Condition): On September 19, 2013 (DOY 263) at 21:38 UTC (15:38 CT), the Landsat 8 satellite entered a ‘safehold’ condition that suspended all data acquisitions. Normal acquisitions resumed on September 21, 2013 (DOY 264).

 

 

Landsat Maneuver Definitions

  • Inclination Adjustment Maneuver (IAM): An IAM is commonly referred to as a Delta-Inclination (Delta-I) maneuver. The maneuver is performed in the cross-track direction (i.e. perpindicular to the direction the spacecraft is moving.) An IAM changes the angle of the equatorial plane to the orbital plane. This type of maneuver is performed periodically (nominally once per year) to maintain the mission's Mean Local Time (MLT). Landsat has a requirement for a MLT equatorial crossing of 10:00 AM +/- 15 minutes.
     
  • Drag Make-Up (DMU) Maneuver: This type of maneuver may also be referred to as a Delta-Velocity (Delta-V) maneuver (or an orbit altitude adjustment maneuver). It is used to raise (or lower) the orbit's semi-major axis. A DMU is a specific type of Delta-V (positive) which increases the orbital velocity thus increasing the orbital altitude and is used to counteract the effects of atmospheric drag on the spacecraft and maintain orbit circulation as well as maintain the strict constraints on the projected spacecraft ground track. (A negative "DMU" is a retrograde maneuver to lower the altitude. However, Landsat 8 has not performed one of these operationally.)
     
  • Risk Mitigation Maneuver (RMM): This type of maneuver is also a Delta-V maneuver to change the orbit altitude. An RMM is executed to avoid orbital debris and may be either a velocity increase (prograde maneuver - semi-major axis increase) or a velocity decrease (retrograde maneuver - semi-major axis decrease). An RMM is only performed if the flight operations team determines the Probability of Collision (Pc) meets certain thresholds as determined by complex conjunction assessments.