Upcoming Unavailability of CDDIS (16-Aug-2002)

The CDDIS will be down from Friday September 13 ~7:00 p.m. through early evening hours of Saturday September 14 for electrical work at GSFC.

GSFC Router Causes Network Outage (16-Aug-2002)

The CDDIS was inaccessible on August 16 from ~12:00 midnight until 9:00 a.m. (EDT) due to problems with a router at GSFC. The network is now operational.

CDDIS Now Official GSAC Wholesaler (05-Aug-2002)

The GPS Seamless Archive Centers (GSACs) are a collection of GPS data archives that exchange information about their individual data holdings to aid users in their search for available GPS data and information. GSAC is currently coordinated by the University Navstar Consortium (UNAVCO). The CDDIS is considered a Data Wholesaler that provides data holding information through anonymous ftp using the current GSAC standard.

GLONASS+GPS Data Archive (11-Jun-2002)

As of June 11, 2002, all GLONASS+GPS data from the IGS IGLOS pilot project will be archived with GPS data in the daily GPS directories: ftp://cddis.gsfc.nasa.gov/gps/data. Data from GLONASS-only receiver data continue to be made available through the ftp://cddis.gsfc.nasa.gov/glonass/data filesystem. More information about the new policy can be found in IGSMail message 3930.

13th International Workshop on Laser Ranging (03-Apr-2002)

The National Aeronautics and Space Administration (NASA), the Smithsonian Institution, and the International Laser Ranging Service (ILRS) are pleased to announce that the Thirteenth International Workshop on Laser Ranging will be held in Washington D.C. during the week of October 07-11, 2002 at the Hyatt Regency Washington Hotel on Capitol Hill. The workshop venue is located in the heart of the nation's capital, offering the visitor easy access to a variety of museums, monuments, restaurants, theaters, concert halls, and other recreational facilities.

Also scheduled during this week will be the Eighth General Assembly of the ILRS and meetings of the ILRS Governing Board and Working Groups. A trip to the Goddard Geophysical and Astronomical Observatory (GGAO) will be arranged to allow attendees to view NASA's prototype SLR2000 system.

Local Organizing Committee:

• John Degnan/NASA GSFC
• Carey Noll/NASA GSFC
• Michael Pearlman/CfA
• Kathy Regul/Westover Consultants Inc.

The organinzing and program committees are currently working on a preliminary agenda and more details which will be provided shortly in the First Circular and the workshop website (http://cddis.gsfc.nasa.gov/lw13). A registration fee of $200.00 (US) plus $40.00 for the banquet will be charged to all attendees. Some in-country financial support will be available for a limited number of attendees.

MLRS Pressure Corrections (14-Mar-2002)

Randy Ricklefs (McDonald Observatory) reports that MLRS data for January 14 0:00UTC through February 16 4:30UTC, 2002 has been resubmitted with corrected barometric pressure values. During this time span the interface between the pressure sensor and the data acquisition computer behaved erratically, giving incorrect pressure readings. Pressure readings were corrected using data from another McDonald Observatory meteorological station. The pressure offset between the two met stations was established from data before and after the problem period. The RMS of the offset between the two met stations is about 1 mB. The SLR normal points' data release flag has been set to '1'. RINEX met data file headers are dated March 11. The MLRS staff regret any inconvenience this causes.

EUROLAS Workshop, March 2002 (12-Feb-2002)

SLR Electronic Mail No. 0890 called for participation in a EUROLAS Workshop at Herstmonceux on "Detecting and Eliminating Errors in the EUROLAS Network". The meeting will take place on 2002 March 11-13 and be very much a hands-on workshop; the suggested agenda is:

• Day 1 pm Detector errors
• Day 2 am Counter/Timer/Timing errors
• Day 2 pm Errors/Detecting errors in reduction/post-reduction processes
• Day 3 am Other error sources
  Simultaneous EUROLAS observing

So far there has been a good response to this proposal, with representatives from five stations planning to attend, plus two representatives from the NASA network. There is room for more attendees though; please do consider whether you could come and contribute to this venture.

Regards,
Roger Wood,Graham Appleby & Philip Gibbs

Error in Pressure Measurement at Maidanak 1864 (11-Feb-2002)

Natalia Parkhomenko reports that prior to the start of 2001 there was a problem with the old meteorological equipment at the Maidanak laser ranging station 1864. In 2001, a new Vaisala RTB 220B met package was installed. The historical barometer was reading low by 6 +/- 2 millibars.

New IP Number for Host cddisa.gsfc.nasa.gov (31-Jan-2002)

At 05:00 p.m. EDT on January 30, 2002, the IP address of CDDIS host cddisa.gsfc.nasa.gov changed from 128.183.102.102 to 128.183.103.97.

Removal of Systematic Bias in Herstmonceux SLR Range Data (30-Jan-2002)

Author: Graham Appleby & Philip Gibbs

REASON FOR CHANGE

We are now confident that we understand the characteristics of a range-dependent range bias that has been in our SLR measurements since 1994 October 1. It is caused by subtle non-linear effects in the Stanford SR620 counters that we use to make the range measurements; the range bias values (amounting for example to some 8-10mm at the distance of LAGEOS) continue to be stable and predictable at a level of uncertainty of about 20ps (3mm in 1-way range).

DATE OF CHANGE

From 2002 February 1 00:00 UT we will apply range corrections to our data before they are submitted to EDC and CDDIS and no further corrections will be required by users.

CONSISTENCY WITH PREVIOUS DATA

For maximum accuracy in interpretation of Herstmonceux (7840) data obtained in the period 1994 October 1 until 2002 January 31 inclusive, the table found in SLRMail message 0891 should be used to determine the appropriate range-dependent correction that must be ADDED TO the time-of-flight given in the normal point data.