STEREO Mission Design and Navigation Review Action Item 2

Closed, June 27, 2006

From: Strikwerda, Tom [Tom.Strikwerda@jhuapl.edu]
Sent: Tuesday, June 27, 2006 4:34 PM
To: David Folta
Cc: Guzman, Jose J.; Dunham, David
Subject: Re: STEREO MDNav AI #2 Response

Thank you Dave! 
Regards, 
----------------------------- 
Tom Strikwerda 
Applied Physics Laboratory/Johns Hopkins University 
240-228-5847 - office 
240-228-0355 - fax 
tom.strikwerda@jhuapl.edu 

On Jun 27, 2006, at 4:29 PM, David Folta wrote: 

  Mike, 

  My response to close the action item. 

  The analysis provided was excellent and shows that the 1 second 
rate does not drastically improve the definitive as I thought it 
might. With this information, we can close the action. 

  Thanks and sorry for the tardiness. 
  Dave 

  At 10:38 AM 5/2/2006 -0400, Michael Mesarch wrote: 

    Dave, here is the response to AI#2 from the STEREO MDNav Review 
from October 12. The original action was "During attenuation near 
perigee, investigate the use of Doppler at a rate of 1 sample per 1 
second versus 1 sample per 10 seconds to help reduce noise". 

    The response from Dr. John Lorah of Honeywell is ... 

    ****************** 

    I went ahead and did some ODEAS runs to look at using 1-second 
data around perigee instead of 10-second data. I re-ran the jobs 
right after P4, called out in Table 6-2 in the latest report. For 
the attenuated spans, I used a 1-second rate, and also increased the 
noise to 3 times the nominal 10-second value. The attached file has 
some detailed results, hopefully not too much info. The short answer 
is that it agrees with our statement that the 1-second rate doesn't 
really help. 

    The four tables in the file have the definitive position, 
    definitive velocity, predictive position, and predictive velocity 
    errors, respectively. The rows in each table are for different 
    runs, with a pair at each of 6, 12, and 24-hours definitive. The 
    first row of each pair is a repeat of Table 6-2, while the second 
    row in each pair is the same thing at the 1-second rate. The 
    shaded column is the total error. Notice that the extra data 
    makes very little difference in general, sometimes making things 
    slightly better, sometimes actually making things worse. I 
    highlighted in red what I think is the most relevant set of 
    numbers. I think the thing that prompted the question was our 
    statements that the definitive velocity around perigee did not 
    meet the 0.1 meter goal in general. Notice that the extra data in 
    the 6 hour case does not put the velocity anywhere near the goal. 

    ****************** 

    See attached file for referenced data. 

    Dave, if you concur with this answer please do so in a reply 
    which cc's Tom Strikwerda, the review chair. Thank you. 

    Michael 

    ********************************* 
    NASA/Goddard Space Flight Center 
    Flight Dynamics Analysis Branch 
    Code 595 
    Greenbelt, MD 20771 

    E-mail: Michael.A.Mesarch@nasa.gov 
    Ph#: 301-286-9917 
    *********************************