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support identification codes (SIC) will be established. Key information including
spacecraft mass, cross-sectional area, drag co-efficient, and solar reflectivity
parameters will be collected. These platform-specific values are needed for accurate
orbit modeling which allows DAS to determine visibility and service schedules up to five
days into the future. In the event these values are not provided, baseline values will be
substituted which will impact orbit modeling accuracy, especially for platforms with orbits
less than 750 km in altitude. DAS Customers with orbit altitudes below 750 km should
update the mass value whenever it varies more than 10% from the previously submitted
value in order to maintain accuracy of their DAS 5-day orbit predictions.
Initial service specification codes (SSC), which will be the basis for allocating resources
and setting up the RF links between the Customer Platform and the TDRSs, will be
established and the required equipment allocation for each SSC will be calculated.
NISN and GDIS access capacity will be determined.
If this analysis indicates that there are insufficient resources to support additional
customers, GSFC Code 450 will determine if additional resources must be procured. A
Project Service Level Agreement (PSLA) will be negotiated with the customer. DAS,
NISN, and SNAS accounts will be established. The Planning activities shown in Table
H-1 ideally take place a minimum of 18 months prior to commencement of services.
H.3 Customer Interface with the DAS
H.3.1 General
Communications between DAS and a MOC Customer involve two different classes of
information. The first type is service data or telemetry, which is the data received from
the Customer Platform and forwarded to the Customer MOC. The other type is a
combination of planning and scheduling information, status information, real-time control
information, and other miscellaneous administrative information.
DAS uses SNAS for all types of communications except the telemetry. The SNAS
interface with DAS allows the customer insight into available resources, allows the
customer to submit requests for DAS services, and permits monitoring DAS service
performance.
Table H-2 lists information exchanged between DAS and the customer via SNAS.
Please refer to Appendix P of this document, or the web site at:
http://snas.gsfc.nasa.gov for further information on SNAS.
Revision 10 H-12 450-SNUG