# Presentation: 596922

## Aura Flight Dynamics

- Joshua Levi
- Lead Flight Dynamics Analyst
- October 27, 2008

## Agenda

**Agenda**

- Re-phasing results
- Risk mitigation maneuvers
- Inclination maneuver planning
- Solid Earth tide model
- Spring 2009 inclination series
- Annual inclination maneuvers
- OMI beta angle request

## Re-Phasing Results

**Re-Phasing Results**

## Phasing Request

**Phasing Request**

- In Spring 2007 the MLS team submitted the request that Aura relocate to a position closer to Aqua
- Analysis began to determine the feasibility of this request
- Final specification received from the MLS team in October, 2007
- MLS team’s primary concern was collecting better science data within the locale of CloudSat observations
- Once approved, the decision was made to halt Aura’s drag make-up maneuver planning processes
- The last drag make-up maneuver within the original WRS-2 ground track control box took place on June 27, 2007
- Aura was allowed to drift forward towards its new ground track control box

## Re-phasing Maneuvers

**Re-phasing Maneuvers**

- Aura performed a 22 second braking maneuver at the center of its new WRS-2 control box on May 8, 2008
- The re-established control box is now +/- 10 Km from a +18 kilometer (East) offset of Aqua’s WRS-2 path
- The first normal drag make-up maneuver within the new ground track error box occurred on June 17th, 2008

|  | Nominal | Maximum | Minimum |
| --- | --- | --- | --- |
| Aura to Virtual Aqua | 480 seconds | 501.5 seconds | 458.5 seconds |
| Aura to Virtual CloudSat | 424.5 seconds | 470 seconds | 379 seconds |

## WRS-2 Ground Track Error

**WRS-2 Ground Track Error**

## Re-phasing Results

**Re-phasing Results**

- The re-phasing of Aura with respect to Aqua performed nominally
- Only exception was the required time to complete the re-phasing due to a lower than expected solar activity
- Braking maneuver was originally planned for April 26, 2008 but low drag altered the maneuver date to May 8, 2008 (12 days later)
- The MLS team has expressed their satisfaction with the science data obtained from the new MLS view relative to CloudSat’s observations

## Re-phasing Results

**Re-phasing Results**

## Re-phasing Results

**Re-phasing Results**

- Zoomed view on next slide

- This plot accounts for the CloudSat pitch offset and a 10km MLS limb height

## Re-Phasing Results

**Re-Phasing Results**

- This plot accounts for the CloudSat pitch offset and a 10km MLS limb height

- CloudSat DMU #12

## Risk Mitigation Maneuvers

**Risk Mitigation Maneuvers**

## RMM Summary

**RMM Summary**

- On June 26, 2008 a decision was made to perform a risk mitigation maneuver
- The maneuver size selected would be the smallest size possible that would still allow Aura to maintain within its -10 kilometer WRS-2 groundtrack limit
- Aura completed DMU #14 on June 17, 2008
- Resulting planned maneuver duration of 2 seconds

## RMM Summary

**RMM Summary**

- Ground Track Error (km)

- Planned GTE trend

- Achieved GTE trend

## RMM Summary

**RMM Summary**

- Due to attitude errors commonly associated with small maneuver durations, the RMM over-performed
- Achieved a low ground track error of -3 kilometers
- Aura maintained its position within its hard WRS-2 limits of +/- 20 kilometers
- The risk posed by the debris was successfully mitigated
- Participating with the FOT and Conjunction Assessment teams for risk mitigation maneuver process improvement

## Inclination Maneuver Planning

**Inclination Maneuver Planning**

## Solid Earth Tides

**Solid Earth Tides**

- Aura FDS has recently acquired the latest version of FreeFlyer which includes a solid Earth tide model
- The inclusion of this model will improve the accuracy of long-term mean local time predictions for the Afternoon Constellation
- Benefits long-term inclination maneuver planning
- Improves FDS’s ability to perform long-term predictions of Aura’s mean local time and beta angle

## Spring 2009 Series Summary

**Spring 2009 Series Summary**

- Afternoon constellation members reached an agreement in March to perform a series of inclination maneuvers in the Spring of 2009
- Aura will perform 9 maneuvers along a similar schedule as Aqua

## WRS Control Box Location

**WRS Control Box Location**

- Aura will perform one drag make-up maneuver to place the spacecraft on a favorable WRS trend prior to its first inclination maneuver.
- At the time of the spring inclination series, Aura will be located in the lower half of its control box with a positive WRS error rate
- All inclination maneuvers will be targeted such that Aura’s WRS will drift towards the controllable side of its control box
- If need be, a small DMU can be performed to keep Aura from violating the top of its control box

## WRS Control Box Location

**WRS Control Box Location**

## Aqua/Aura Inclination Maneuver Calendar

**Aqua/Aura Inclination Maneuver Calendar**

## Inclination Maneuver Schedule	

**Inclination Maneuver Schedule****	**

- These maneuvers were planned using the historic performances of inclination maneuvers #5 through 12 (Fall 2006 and Spring 2007)
- Performance figures include thrust scale factors, duty cycles, and slew out/back durations

## Inclination Maneuver Locations

**Inclination Maneuver Locations**

## Predicted Maneuver Results

**Predicted Maneuver Results**

- Aura’s 9 inclination maneuvers in the Spring of 2009 are expected to produce:
- Total maneuver delta-V: 12.794 meters/second
- Total maneuver delta-I: -0.0957 degrees
- Total mass depletion: 21 kilograms
- Hereafter our nominal plan is to perform inclination maneuvers on an annual basis

## Annual Inclination Maneuvers

**Annual Inclination Maneuvers**

- Inclination maneuvers in Spring 2010 will assist Aura in satisfying the OMI beta angle request
- Without annual inclination maneuvers, Aura’s beta angle will pass outside of the OMI request
- This would require a large series of maneuvers in 2011 in order to meet the OMI request in future years (on the order of 12 maneuvers)
- Performing annual inclination maneuvers would allow the OMI request to be continually satisfied
- Decreases the amount of maneuvers we would otherwise perform on a biannual basis

## Annual Inclination Maneuvers

**Annual Inclination Maneuvers**

**Aura Upper Limit = 36****°**

**OMI Upper Request = 31.2****°**

**Aura Lower Limit = 16****°**

**OMI Lower Request = 18.3****°**

**9 maneuvers**

**inclination maneuvers**

**inclination maneuvers**

**inclination maneuvers**

## Annual Inclination Maneuvers

**Annual Inclination Maneuvers**

**Mean Local Time at the Ascending Node (hrs)**

**9 maneuvers**

**14:00**

**13:54**

**13:48**

**13:42**

**13:36**

**13:30**

**inclination maneuvers**

**inclination maneuvers**

**inclination maneuvers**

## Annual Inclination Maneuvers

**Annual Inclination Maneuvers**

- The concept of annual inclination maneuvers was introduced to other missions at the latest Afternoon Constellation MOWG on October 9
- Advertised performing 3 to 5 inclination maneuvers in the Spring of 2010
- 3 inclination maneuvers in Spring 2010 will satisfy the OMI beta angle request in the Fall 2010
- Performance of 2009 series?
- Residual errors with solid Earth tide model?
- Easier for other Constellation members
- 4 inclination maneuvers in Spring 2010 provides a small amount of “buffer” between Aura and the OMI request
- Our current plan. Delivered for review to other members
- Increased difficulty for other Constellation members

## Annual Inclination Maneuvers

**Annual Inclination Maneuvers**

- Zoomed view on next slide

## Annual Inclination Maneuvers

**Annual Inclination Maneuvers**

**OMI Upper Request = 31.2****°**

- 3INC maneuver case

- 4 INC maneuver case

## Backup Slides

**Backup Slides**

## Annual Inclination Maneuvers

**Annual Inclination Maneuvers**

**Mean Local Time at the Ascending Node (hrs)**

**14:00**

**13:54**

**13:48**

**13:42**

**13:36**

**13:30**

## Old MLS/CPR Interaction

**Old MLS/CPR Interaction**

- CPR Observation

- MLS Observation

- Aura Location

- CloudSat Location

- MLS to CPR Observation Separation

## New MLS/CPR Interaction

**New MLS/CPR Interaction**

- CPR Observation

- MLS Observation

- Aura Location

- CloudSat Location

- MLS to CPR Observation Separation