| Date: | 2000-03-17 09:06:00 | |
| Sender: | Julie Horvath, Scott Wetzel, NASA SLR <Horvath, Julie E. <Julie.Horvath@honeywell-tsi.com>> | |
| Subject: | [SLR-Mail] No. 569: Daily Updated Acquisition Data | |
| Author: | Julie Horvath, Scott Wetzel, NASA SLR | |
| Content: | ******************************************************************************** SLR Electronic Mail 2000-03-17 09:06:00 UTC Message No. 569 ******************************************************************************** Author: Julie Horvath, Scott Wetzel, NASA SLR Subject: Daily Updated Acquisition Data Dear Colleagues, Recently, there has been much discussion of acquisition data products that are provided to the SLR community, particularly with very low orbit satellites. With the altitude of some important upcoming missions being quite low, a need for more accurate and timely predictions is becoming critical. NASA and Honeywell Technology Solutions Inc (HTSI, formerly ATSC) have been working on a solution for a more timely and accurate acquisition data product. This idea has received the endorsement of the ILRS Central Bureau. NERC has been delivering daily IRVs for the GLONASS and GPS satellites and has maintained daily acquisition products for some time, while HTSI has continued with the weekly distributions on an operational basis. In response to the ILRS request to improve acquisition data, HTSI will replace the weekly distribution of SLR predictions with a daily distribution of updated predictions. HTSI has been providing this data product for approximately three years as a pilot project to the MLRS system in Texas and to the NASA 48” facility at Goddard with great success. These daily predictions will be automatically generated and distributed and will be available on the ftp sites of the CDDIS and the EDC daily. The distribution of these new acquisition data will begin next week on 3/23/00. Some key points about this new data product include: 1. This data will REPLACE the weekly distributions of TIV´s currently provided, therefore weekly distributions will no longer be made. 2. This acquisition data is identical in format and structure to the product that you currently receive weekly therefore no software modifications will be required on your station to utilize the new predictions. 3. The new acquisition data will include 6 days of Tuned IRV´s every day beginning with the current day. 4. Daily acquisition data will be generated for all ILRS scheduled satellites (including ERS-1, ERS-2, WESTPAC, and CHAMP). 5. Ephemeris numbers will be incremented daily whether or not new SLR data has been introduced into the orbital solution. 6. The new updated daily IRV files will be transmitted between 14:00 and 17:00 GMT every day. (A more specific time of day will be determined after initial implementation) 7. The CDDIS will post the new daily IRV´s on the ftp site ftp://cddisa.gsfc.nasa.gov/pub/predicts/yyyy/satname where yyyy is the 4-digit year and satname is the name of the satellite. 8. The EDC will post the new daily IRV´s on the ftp site ftp://ftp.dgfi.badw-muenchen.de/pub/laser/predictions/. 9. Maneuver messages (for GFO-1 and TOPEX) will be as they are under existing procedures. These messages and acquisition data may arrive at any hour of the day. 10. If no SLR data has been acquired following a maneuver before the generation of the TIV for the next day, there may be an occurrence when no acquisition data (for that satellite) is sent for a particular day. If this occurs, then we expect that the previous day´s data is still valid and should be used to acquire the satellite. One of the key benefits of the new data products is that the most recent SLR data will be used every day to generate predictions. Also, time bias for all satellites will be very close to zero every day and no time bias correction will be necessary. This will be very important for the new lower orbit satellites, but will also be a great benefit for the current satellites. As this new data is made available, we appreciate any or all comments regarding the use and quality of tracking that is produced from this new acquisition product. Enhancements of this product will surely be necessary, and we anticipate and appreciate your support. Thanks and regards, Julie Horvath Scott Wetzel NASA SLR Honeywell Technology Solutions Inc. (301)805-3951 julie.horvath@honeywell-tsi.com scott.wetzel@honeywell-tsi.com From: ”Horvath, Julie E.” ******************************************************************************** |