Findings & Concerns

Meeting of June 11, 2002
Sounding Rocket Working Group
National Aeronautics and Space Administration


I.  Existing Technology Currently Undergoing Augmentation

A.  Coarse Attitude Determination and Control

Improving both coarse attitude control and attitude knowledge continues to constitute an important dialogue among the SRWG, the SRPO, and NSROC.  The SRWG is pleased that NSROC is dedicating resources to improving the situation, as evidenced by the presentation by NSROC at the last meeting.  The SRWG has the following remarks relative to the current situation and future plans:

1.       Post-flight attitude determination.  The SRWG is pleased that NSROC recognizes the need to improve over past performance.  The goal must be to provide accurate, routine, and easily interpretable attitude data to the scientists so they can analyze their data without the need to carry out extensive (and expensive) efforts on each payload simply to determine where it was pointing.  The NSROC presentation of 11 June 2002 shows that improvements have been made in the visualization of gyro data and that work is underway to verify gyro solutions using other simultaneous on-board measurements (e.g., magnetometers).  It is clear that many adjustable parameters (e.g., gyro drift, unmeasured magnetometer offsets, and non-orthogonality matrices) are used in the current paradigm.  The SRWG would like to work with NSROC to better understand how these parameters are used and what magnitudes are ascribed to them for a given flight.  We commend NSROC for embarking on this path and look forward to the day when such verifications are routine.

2.       Replacement of Space Vector systems.  The replacement of the Space-Vector supplied systems (gyros and coarse inertial and magnetic ACS units) is of paramount importance and urgency.  The SRWG is alarmed that this replacement has been allowed to fall behind to the point that it is not clear whether missions currently awaiting design review will use Space Vector systems or newly-developed NSROC systems.  We urge both SRPO and NSROC to place a high priority on this activity.

3.       Miniature Daytime Attitude Sensor  --  “NSROC(a)”.  On their own initiative, NSROC has placed a high priority on the development of a new, miniature attitude knowledge system called “NSROC(a),” although the motivation is not apparent to the SRWG.  The most mature aspect of the NSROC(a) system is its use of a sun sensor to determine attitude.  This sensor works only for daytime flights, which account for only a small fraction of the experiments that utilize coarse attitude.  A horizon sensor will be substituted for nighttime flights.  Both sun sensors and horizon sensors have been used by the Wallops rocket program for decades and have not proven to be as reliable as the gyro for providing accurate and routine attitude data to the experimenter.  Since the NSROC(a) system has now been flown on numerous payloads, presumably each time as a test bed, we would like to know how well it has performed with respect to its absolute accuracy  --  e.g., body azimuth, elevation, and roll position (or Euler yaw, pitch, and roll) relative to a fixed reference system on the earth.  In this regard, traditionally, absolute roll position has been the most difficult parameter to reliably ascertain (to within 1 degree), whereas body elevation and roll rate are comparatively simple.

The SRWG is puzzled as to why the NSROC(a) has received a priority in development.  We believe that the developments most urgently needed in coarse attitude systems should emphasize replacement (and improvement) of the capabilities now provided by the Space Vector gyro systems.  We wonder if the development of the NSROC(a) has been largely driven by the applicability of this system to non-NASA missions.

B.  Fine Pointing ACS and the StarTracker 5000

The SRWG is concerned about the lack of progress toward implementing the ST5000 fine pointing star tracker (which has been discussed at several previous SRWG meetings) as well as the apparent reluctance of NSROC to fully investigate its potential for Lost-in-Space (LIS) tracking.  The report of the flight performance of the ST5000 from last December is encouraging, despite the failure of the camera lens.  However, no additional test opportunities were discussed or appear to be scheduled except for the initial flight of the University of Wisconsin FUSP payload in late 2003.  This schedule is troubling, because of the importance placed by both the SWRG and NSROC on transitioning from the aging Ball trackers to a more modern system.

The SRWG expects the ST5000 to provide a dramatic improvement in attitude control by permitting the targeting of fainter guide stars and potentially the direct acquisition of the star (science) field without slewing between two fields (via LIS mode).  The latter capability has the potential to increase time available for science operations by 10% or more.  The ST5000 also represents a physical change from the Ball trackers. Several members of the science community are also in the design phase of new experiments where they must make the decision as to whether they can use the ST5000 or must make the necessary compromises to accommodate the existing units.

The SRWG believes that the approach to the development of the ST5000 could be greatly improved.  Funding levels are low, timelines are ill defined, and only minimal NSROC resources appear to be committed to this urgently needed, valuable sub-system.  This compares poorly with the effort level expended on the NSROCa system, for example, which the SRWG regards as having much lower priority than the ST5000.  In this regard, the SRWG make several specific recommendations:

     1.  An implementation plan for the ST5000 should be developed that clearly outlines the roles that NSROC and the University of Wisconsin (UW) will play in the flight qualification of the ST5000.  This should include a timeline of development including potential test launches, stages of use (Ball replacement only, followed by LIS), and a target date for the replacement of the Ball tracker.

A line of communication between NSROC and experimenters should be opened concerning the availability of the ST5000 for testing.  Many community members are willing to support test flights that advance this program.

A feasibility study with UW should be conducted concerning the different ways in which LIS tracking can be used with the existing ACS and what costs would be involved.

C. DS-19 and the S19-D Guidance System

The SRWG shares NSROC's and White Sand Missile Range’s (WSMR's) concern over the recently identified possibility of a Black Brant IX vehicle exiting the range boundaries in the event of a hardware failure on the DS-19 that results from a ``hardover'' canard condition after T+15 seconds.  Range safety is the highest priority of any mission and the possibility that a vehicle could exit the range within the 3 second window required for the missile flight safety officer to activate the command destruct is cause for the highest concern.

However, the SRWG points out that the envisioned solution, namely restricting the control loop to the old S19 control loop (guidance through T+15 seconds), is not the only possible solution.  We note that at least four other solutions were proposed after NSROC's DS-19 return-to-flight presentation at the June 11 SRWG meeting.  These included:  (1) computer activation of the command destruct issued from the ground; (2) autonomous destruct issued from the vehicle; (3) a canard hardover condition detect and cable cutout system; and (4) a creeping canard angular range restricter that gradually reduces canard authority towards the end of the burn where the full angular range is not required for control.

The SRWG believes that at the present time the parameter space for a possible solution has not been fully explored.  We also believe that reverting to the old S19 control loop is a waste of a highly desired feature of the DS-19, namely full guidance through Black Brant burn-out and the resulting low impact dispersion, which is in-and-of-itself a safety feature. Hence, we strongly recommend that NSROC and WSMR pursue a solution for the full return of DS-19 capability (full guidance through BB burnout at T+44 seconds)that will provide the required safety margin for missile flight safety. 

II.  New Technology Currently Being Implemented at Wallops

A.  GPS Based Altitude Event Triggers

The SRWG applauds NSROCs proactive development of the GPS Event Module (GEM) by the telemetry group.  This technology has the potential to significantly increase the observing time for science payloads.  The experimenter will no longer have to make conservative estimates based on historical booster performance to set timer events with large (2 or 3 sigma) margins.  This allows instruments to turn on, open doors, deploy booms, or begin maneuvers and observations earlier than with timer events. Similarly on descent, the GEM allows experiments to be shut down and parachutes deployed at a later time than conservative timer settings would have allowed. Finally the GEM obviates the need for experimenters to include altitude sensors as fail-safes or event triggers in their payloads, reducing cost and complexity.  This is potentially a major development by NSROC and promises to be a great benefit to the experimenter.  That said, the SRWG would like to see more information on this system including reliability estimates and data, the possibility of adding redundancy and how exactly the traditional timer events will be used as backups.  The system will not add value to the experiment unless the timer backups are set using optimistic values for motor performance.  Thus redundancy and reliability are keys for making this highly desirable technical development a success for science payloads.

B.  Patriot Rocket

The SRWG was very pleased to learn of the recent development of the Patriot rocket to provide an alternative launch system to the Brant, including both the single stage Brant and the Terrier Brant system.  In addition to the higher performance (i.e., broader payload capacity), the cost savings are important for the program overall.  We look forward to more information concerning the introduction of the Patriot rocket into NASA’s inventory.

C.  Advance Engineering Computer Design

The SRWG applauds the use of state-of-the-art advanced engineering computer aided design tools (e.g., SolidWorks@3D) in the mechanical design of payloads.  Such software provides a better design, saves time, and calculates mass properties and other engineering parameters.  Furthermore, by encouraging the users to submit their experiment lay outs in the same (or compatible) computer packages, the payload design is not only improved, but also fit checks can be made on the computer and the design optimized in a more efficient manner.

III.  Technology for the Future

A.  Technology Roadmap 

The SRWG is encouraged by the efforts that WFF has made recently concerning implementation of new technology and new techniques, and updating of older hardware.  We are concerned, however, that if undirected and unplanned, these efforts may not be used to optimally advance the research efforts of the NASA science community.  Further, we recognize that NSROC may focus on developing technology that enhances their ability to acquire non-NASA new business at the expense of the NASA science community needs.  We would like to better understand how NSROC delineates, if at all, between R and D efforts for NASA projects and those, for example, for DoD.  Are their development resources for each effort that are accounted for separately?

From the perspective of the NASA research scientist, the insistent science requests for "more time on target" and "more and smaller sub-payloads to higher altitudes" appear to be most effectively addressed with innovative hardware and clever software.  Indeed, the NSROC engineers can implement just about anything, given enough time and money.  However, a balance must be struck between the endless requests of scientists and the limited resources of engineering design time and funds for prototypes and testing. 

To achieve such a balance we look to the NASA Sounding Rocket Program Office (SRPO).  One way of organizing such information is a technology "roadmap".  Inputs to this roadmap include (a) science needs requests from the user community, including priorities, and (b) engineering technology ideas and possibilities from the NSROC engineering community, including costs.  The output of such a roadmap from the SRPO should be a balance between the urgency of the science need and its expected scientific impact in the community, and the costs of the engineering implementation.  An important consideration is the length of time needed to implement the new technology, as some small projects can be completed quickly to meet a specific goal and other longer-term developments can be done more slowly and in parallel.  Such a roadmap, once initiated, should be perpetuated as a "living document", wherein NSROC engineers (or others) can post potential new technology ideas, and scientists can post wish-lists. 

At the last meeting, the SRPO stated its intention to facilitate this endeavor.  The SRWG fully endorses this initiative and believes that the SRPO is uniquely suited to both create and monitor a sounding rocket technology roadmap, matching up needs and possibilities, and optimizing the use of our limited community resources.  For our part, we believe that the SRWG can help define and communicate scientific user input to the roadmap.  We look forward to working with the SRPO on this exciting new aspect of the program.

B.  The “Big Gun”

The ability to fire small ballistic payloads from a large gun, developed by the DOD during the 1960's, presents potentially significant new capabilities to NASA's suborbital program, particularly with regard to lower thermospheric/ionospheric and mesospheric investigations requiring multiple payloads launched at regular intervals over a period of several hours or several days.  The proposed gun launcher augments a particular strength of the sub-orbital program  --  namely providing the only means of directly sensing the region of the earth’s upper atmosphere between 40-180 km. Furthermore, the types of experiments made possible by this technique loom important as NASA-sponsored researchers are pressed to better understand space weather and climatology of this region and others. 

The SRWG heard an excellent presentation introducing the idea of using the large gun and some of the expected science return if it could be returned to use as a scientific investigative tool.  The SRWG strongly recommends that NASA undertake a feasibility study to determine whether it is possible to return the remaining big gun (in Yuma, Arizona) to operation, and what are the costs of doing so.  This  study should be conducted as soon as possible, because DOD support of the facility may lapse in the near future.  This implies that urgent action may be needed in order to preserve the facility and make it operational.

IV.  Welcome To Phil Eberspeaker

The SRWG extends a very warm welcome to the new Chief of the Sounding Rocket Program Office, Mr. Phil Eberspeaker.  Many of us remember Phil as a payload manager and as the leader of the development team that helped implement NSROC.  We believe that Phil Eberspeaker is very well qualified to serve as the Chief of the Sounding Rocket program.  He brings much knowledge of how sounding rockets work, management skills necessary to keep the program on course, and leadership skills to guide the program to new and fruitful directions.  The SRWG looks forward to working with Phil to advance the unique scientific research tools that sounding rockets provide to the nation’s space program.


NASA Sounding Rocket Working Group

Dr. Robert F. Pfaff, Jr. (Chair)
NASA/Goddard Space Flight Center

Dr. James Clemmons
Aerospace Corporation

Dr. Joseph Davila
NASA/Goddard Space Flight Center

Dr. Walt Harris
University of Wisconsin

Dr. James LaBelle
Dartmouth College

Dr. Kristina Lynch
University of New Hampshire

Dr. Stephan McCandliss
Johns Hopkins University

Dr. Scott Porter
NASA/Goddard Space Flight Center

Dr. Charles Swenson
Utah State University

Dr. Erik Wilkinson
University of Colorado