A Final Letter
Friday 20 Feb 2004
Hello all-
Thanks to all of you for following the Sersio campaign
with such enthusiasm. I have had many requests to
summarize the "well, did it work?" question so here's
an attempt. Overall: the launch event was beautiful,
much more than we had hoped for; the trajectory was
perfect and the motors in fact overperformed, bringing us
about 9 km higher (which is always better) than expected;
the rocket was tracked and full data was received from
multiple telemetry sources; ground camera and radar data
provide a beautiful framework for the in situ measurements;
in fact in turns out that there was a serendipitous DMSP satellite
pass across the event only 10 minutes before the launch; all
onboard instruments returned data; but.... there was a major
malfunction of one of the onboard payload subsystems so
many of the onboard measurements are heavily compromised.
The ACS (attitude control system), a set of gas thrusters
used to point the payload (after the motors are done firing)
in a particular attitude, was supposed to align the spin axis
of the payload to the local magnetic field line so that
(a) the payload would not precess/nutate, (b) the particle
detectors could look up and down the field line, and (c) the
onboard camera could see aurora at the footpoint of the local
field line. However, somewhere in the payload development or
buildup something went wrong, and the net effect of the ACS
efforts was to push the payload away from the field line direction,
and also to aggravate rather than mitigate precesssion. Thus
the payload ended up in what is called a "flat spin", where the
body is rotating around the wrong axis and lying on its side.
As a result, the camera and particle detectors are looking
sideways, the payload motion is unstable, and the various
deployments (booms, subpayload) got messed up. At the moment
we are working hard to assess what quantitative data
we can retrieve from the onboard measurements. An analogy would
be a video camera mounted on the front of a car which suddenly
goes into a tailspin; we need to figure out which way we are
looking and what we can see.
So, it is very hard at the moment to answer the questions
"did it work?" and "are you happy?" and even "what will you
learn?". As you can see from my first paragraph, many things
did work, and worked well. Certainly we will learn a lot about
the type of dayside reconnection and ion outflow event into
which we launched. Certainly we are unhappy about the
compromised onboard data. But we're certainly not ready to say
just how bad, or how good, it is. We'll post updates to the
Sersio webpage (www.dartmouth.edu/~aurora/sersio.html) and you
can follow our progress there; we have already posted preliminary
summaries of the onboard data, and there are links to the
groundbased and other data as well. I hope that this launch
campaign email series has been an interesting adventure for
you. Now we will put our heads down and get to work on
reducing the data into science.
-K
