[X] My Assistant

[nprev]

The spacecraft has entered its preliminary design review phase, so I think it's time to begin discussion of what promises to be a fascinating journey to one of the most interesting destinations in the Solar System. Dr. Robert Pappalardo, the mission's chief scientist, delivered an overview of Europa as well as a top-level description of instrumentation and objectives during a talk tonight at the Griffith Observatory as part of their monthly "All Space Considered" series, so that serves as a good starting point. His presentation starts at 29:35.

As a reminder, please carefully review rule 1.3 before commenting. In fact, please review all of them. Thanks!


Europa Clipper Presentation (29:35)

[mcaplinger]

Here's a quick edit of the specifics about the MOSFETs from the automatically-generated captions from the today's press conference. Any errors not part of the autogeneration are mine.

As soon as we had learned that there might be an issue with our
transistors, which was back at the beginning of May at JPL, we moved
quickly as a project and as a lab and agency with our partners as well
to quickly analyze the risks and conduct tests. [We] generated
tremendous amount of data. We know a lot about the the Jupiter
radiation environment from previous NASA missions including the
current Juno Mission which is at Jupiter right now.

We completed extensive testing to validate the transistors on the
spacecraft. We ran tests 24 hours a day over the last four months at
multiple locations at the Jet Propulsion Laboratory, at the Applied
Physics Laboratory and at the NASA Goddard Space Flight Center. We
simulated flight like conditions to illuminate any issues that the
transistors might have over our four-year science Mission across the
variety of applications we have on the spacecraft.

We put these representative transistors into these environments,
radiated entire circuits and to see how the system behaves and not
just the transistors themselves. We looked at transistor temperatures
while the spacecraft was outside of Jupiter's most intense radiation
environment to determine how much recovery we might be able to get
from these transistors while we're not in that intense radiation
environment. After each flyby we've replicated that transistor
self-healing, or annealing as it's called, that occurs by heating them
to room temperature while they they essentially rest far from that
intense radiation environment as we go around each orbit of Jupiter
before [coming back to] Europa again.

The underlying issue was that there was a gap in how industry
qualifies the kind of hardware like MOSFETS for high radiation
environments. The parts in question, the semiconductor in the
transistors are cut from silicon wafers and those silicon wafers met
the radiation hardness requirements that we needed, but then those
semiconductor Wafers degraded while in storage. We concluded after
all of this testing um that during our orbits around Jupiter while
Europa Clipper does dip into the radiation environment, once it comes
out it comes out long enough for those transistors the opportunity to
heal and partially recover between flybys. we're going to continue to
closely monitor the both the radiation environment we have a radiation
monitor on board as well as the performance of the transistors from
the ground once we are in flight and once we arrive at the Jupiter
system to accomplish this. we've received help from many corners
including the vendor. the vendor's been immensely proactive and
helpful throughout all of our work.

To reiterate what's already been said we can and I have very high
confidence, and the data bears it out, complete the original mission
which is 49 flybys of Europa and amounts to 80 orbits of Jupiter...

As Jordan said, they have margin and we have no reason to to expect
anything other than a great four years and an extended mission beyond
that.

[john_s]

Launch delay, due to Hurricane Milton’s impending arrival over Cape Canaveral on Wednesday, the day before the launch window opens. Blog post. Frustrating (for those of us already in Florida), but the launch window is several weeks long so we’ll be patient.

John

[Bjorn Jonsson]

Probably frustrating for everyone. But I wonder if not launching at the start of the several week launch window results in fuel savings. Back in 1997, Cassini was launched on October 15 instead of October 6 (the start of the launch window). This was due to a problem with Huygens. The delay resulted in some fuel savings. If I understand correctly, launching at the start (or end) of the launch window usually requires slightly more fuel for trajectory corrections (esp. long burns like deep space maneuvers).

[mcaplinger]

If I understand correctly, launching at the start (or end) of the launch window usually requires slightly more fuel for trajectory corrections (esp. long burns like deep space maneuvers).

Usually the optimum is in the middle of the launch period (more or less by definition), but I haven't seen any quantitative discussion of this specific case. See https://ntrs.nasa.gov/citations/20160008162 for an old analysis of the 2021/2022 launch periods -- that 2021 launch was from 15 Nov to 5 Dec and optimal was 24 Nov.

It's typically a small, probably negligible, difference.