The ACE S/C is safe and in science data collection mode.

On April 3, 2000 (day 94) the Ultra Low Energy Isotope Spectrometer (ULEIS)
instrument experienced an anomaly involving a portion of the sensor's
operation. The anomaly was detected from processed science data.
Specifically, the rates on the front micro-channel plate (MCP)
system decreased substantially and abruptly.  This decrease has persisted
through the time of the most recent data available from the ASC (day 109).
This MCP produces the start pulse for ULEIS time-of-flight (TOF) system 1.
Although we are using primarily TOF system 2, which derives it start pulse
from a separate (middle) MCP in the sensor, this anomaly does degrade the
capability of the instrument to resolve isotopes since data from TOF system 1
is used to fine tune the data from TOF system 2.  No other aspect of the
instrument's operation has been affected.  All of the rate channels and pulse
height channels with atomic species resolution are fully functional. All other
electronic functions, voltages, and data processing operations are nominal.
The ULEIS team is presently actively engaged in diagnosing this problem.

All other ACE science instruments are functioning normally.