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XTENEWS: PCA Gain Epoch 4, and other items

               The Beginning of RXTE PCA Gain Epoch 4
			and other news items

RXTE Users:

This message contains information on the following topics:
	The beginning of Gain Epoch 4 (March 22, 1999)
	Bit errors in RXTE data, March 14-18 1999
	Rex: Easy Basic Reduction of Multiple Observations 
	Other Software News
	Heads-Up: Cycle 5 Announcement due for release Apr 30

Gain Epoch 4

At 16:30 on March 22, 1999, all 5 PCUs on board RXTE were commanded to
a lower high voltage setting, marking the dawn of Gain Epoch 4. The
change was made after PCU 2 began to suffer breakdown events, similar
to those seen in PCUs 4 and 5.  From now on, PCU 2 will regularly be
'rested', following the practice already established for PCUs 4 and 5.

Calibration observations were performed after the gain change, and
preliminary Epoch 4 response matrices are available from the PCA Web
pages (accessible from the GOF homepage, http://rxte.gsfc.nasa.gov/ -->
"Data Analysis" --> "Calibration Information").

Between March 23-25, a few intervals exist during which PCUs 4 and 5
were operated at the 'old' Epoch 3 voltages, leading to 'mixed gain'
data files. Details of these intervals can be found on the XTE Big
Events List (GOF homepage --> "SOF" --> "Significant Events"). 
Affected PIs have been notified directly.

Bit Errors: A Faulty Memory Card

Between March 14, 7 UT and March 18, 18 UT RXTE was operating with a
faulty memory card that led to some corrupted data. The problem was
isolated to half of one of seven cards and the memory was remapped
around that area (7% of the total). We believe that only a small part
of the data is affected and are trying to determine the impact. We are
evaluating whether it will be necessary to repeat observations which
occurred during this time.

Once the impact of this event on recent data is known, we will post
more information on the GOF Web pages. If analyses show that any data
are potentially corrupt, the appropriate PI's will be contacted
directly and arrangements made to reschedule the observation, should
that prove necessary. We hope to have more information on this
situation soon. 

Rex: Easy Basic Reduction of Multiple Observations 

Analyzing large numbers of PCA observations from a single proposal
just got easier! Rex, a new script which operates on multiple
observations within a given proposal, is now publicly available to the
user community in a beta-test form. Now, issuing one command results
in the generation of the appropriate filter files, basic GTIs,
extracted Standard2 spectra, and background estimation, as well as
background-subtracted net light curves for each ObsId, and for the
proposal as a whole. See the Rex recipe in the RXTE Cook Book
(http://rxte.gsfc.nasa.gov/docs/xte/recipes/cook_book.html) for
instructions on downloading the relevant files, and running the

Other Software News

FTOOLS 4.2 was released on December 10, 1998; by now, all users should
have installed it for RXTE analysis.  On the "Calibration Information"
page referenced above, we include a bug fix for PCARSP V2.37 in this
distribution, to assure Y2K readiness.

Users are warned that the two tools PCADTLC and PCADTSPEC contain
flaws rendering the deadtime correction invalid, particularly in cases
where not all PCUs are on. Work is proceeding to resolve this issue.

Cycle 5 is on the way!

Heads-up: the fifth cycle of RXTE observing will begin on or around
Jan 1, 2000, and last for 12 months. The Announcement soliciting
observing proposals for participation in Cycle 5 is expected to be
released on April 30th 1999, with a due date of July 30th. Time to
start thinking about the next round ... and note that due to the gain
change, many proposers may need to redo their source count rate and
telemetry estimates. More about this in a later message.

If you have any further questions about these developments, please
contact the RXTE GOF at xtehelp@athena.gsfc.nasa.gov.

| Dr. Alan P. Smale                | xtehelp@athena.gsfc.nasa.gov (RXTE)|
| RXTE Guest Observer Facility     | alan@osiris.gsfc.nasa.gov (me)     |
| Code 662,  NASA/GSFC             | (301) 286-7063 (voice)             | 
| Greenbelt, MD 20771, USA         | (301) 286-1682 (FAX)               |
|              RXTE GOF homepage: http://rxte.gsfc.nasa.gov/            |

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