EXECUTION COPY

                          THIRD SUPPLEMENTAL INDENTURE


         THIRD SUPPLEMENTAL INDENTURE (the "Third Supplemental Indenture") dated
as of March 7, 2003 between Sirius satellite radio inc. (formerly known as CD
Radio Inc.) (the "Company") and HSBC Bank USA, as trustee (the "Trustee").

         WHEREAS, the Company and The Bank of New York (as successor to U.S.
Trust Company of Texas, N.A., "BONY"), as trustee, are parties to a first
supplemental indenture, dated as of September 29, 1999 (the "First Supplemental
Indenture"), to the indenture dated as of September 29, 1999 (the "Original
Indenture") between the Company and BONY, and the Company and the Trustee are
parties to a second supplemental indenture, dated as of March 4, 2003 (the
"Second Supplemental Indenture" and together with the First Supplemental
Indenture and the Original Indenture, the "Indenture"), to the Original
Indenture;

         WHEREAS, pursuant to the Indenture, the Company has issued the 8 3/4 %
Convertible Subordinated Notes due 2009 (the "Securities");

         WHEREAS, Section 9.2 of the Indenture provides that the Company, when
authorized by a resolution of the Board of Directors, and the Trustee, with the
consent of the holders of not less than a majority in principal amount of the
Securities outstanding, may amend the Indenture;

         WHEREAS, the Company has heretofore delivered or is delivering
contemporaneously herewith to the Trustee a copy of the Officers' Certificate of
the Company authorizing the execution, delivery and performance of this Third
Supplemental Indenture; and

         WHEREAS, all conditions necessary to authorize the execution and
delivery of this Third Supplemental Indenture and to make this Third
Supplemental Indenture valid and binding have been complied with or have been
done or performed.

         NOW, THEREFORE, in consideration of the foregoing and notwithstanding
any provision of the Indenture which, absent this Third Supplemental Indenture,
might operate to limit such action, the Company and the Trustee agree as follows
for the equal and ratable benefit of the Holders of the Securities:

                                   ARTICLE I
                                   DEFINITIONS

         Section 1.01 General. For all purposes of the Indenture and this Third
Supplemental Indenture, except as otherwise expressly provided or unless the
context otherwise requires:

                 (a) the words "herein", "hereof' and "hereunder" and other
words of similar import refer to the Indenture and this Third Supplemental
Indenture as a whole and not to any particular Article, Section or subdivision;
and

                 (b) capitalized terms used but not defined herein shall have
the meanings assigned to them in the Indenture.




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                                   ARTICLE II
                                   AMENDMENTS

         Section 2.01 Amendments. The Indenture is hereby amended in the
following respects:

                 (a) Section 6.01(5) of the First Supplemental Indenture is
                     hereby deleted in its entirety.

                 (b) Section 6.01(6) of the First Supplemental Indenture is
                     hereby deleted in its entirety.

                 (c) Section 6.01(7) of the First Supplemental Indenture is
                     hereby deleted in its entirety.

                 (d) Section 6.01(8) of the First Supplemental Indenture is
                     hereby deleted in its entirety.

                 (e) Section 6.02 of the First Supplemental Indenture is hereby
                     amended by deleting the parenthetical phrase, "(other than
                     an Event of Default specified in Section 6.01(7) or (8))"
                     in the first sentence thereof.

                     Section 6.02 of the First Supplemental Indenture is further
                     amended by deleting the following sentence in its entirety:

                        "If an Event of Default specified in Section 6.01(7) or
                        (8) occurs, the principal of, and accrued interest on,
                        all the Series 8 3/4% Notes shall automatically, and
                        without any declaration or other action on the part of
                        the Trustee or any Holder, become immediately due and
                        payable."

                     Section 6.02 of the First Supplemental Indenture is further
                     amended by deleting the reference to Section 6.13 in clause
                     (2) thereof and replacing it with Section "5.13".

                 (f) Defined Terms; Related Amendments. Any and all defined
                     terms used solely in the sections, subsections,
                     subparagraphs or provisions of the Indenture deleted by
                     Sections 2.01 (a) through (e) this Third Supplemental
                     Indenture are also hereby deleted. Any provisions contained
                     in the Securities that relate to any sections of the
                     Indenture that are amended by this Supplemental Indenture
                     shall be likewise amended so that any such provisions
                     contained in the Securities will conform to and be
                     consistent with such amended provisions of the Indenture.

                                  ARTICLE III
                                     WAIVERS

         Section 3.01 Waiver of Defaults and Events of Default. The Company
represents and warrants to the Trustee that Holders of the Securities issued
under the Indenture have irrevocably and unconditionally waived, in accordance
with the terms of the Indenture, (1) any failure by the Company to comply with
any term, covenant, provision or condition of the Indenture and (2) any defaults
and events of default under the Indenture (other than, with respect to those
Holders of the Securities who have not waived their right to receive the payment
of such interest, interest payment defaults, which unwaived interest payment
defaults the Company shall remedy within 10 days after the date hereof), in
existence at the time of the filing of the Registration Statement on Form S-4
(File No. 333-101317), as amended (the "Registration Statement"), including
those arising from representations and warranties made or affirmed in connection
with the delivery of compliance certificates, whether or not such defaults and
events of default are related to the restructuring (as described in the
Registration Statement) or caused by the recapitalization plan (as described in
the Registration Statement).


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                                   ARTICLE IV
                                  MISCELLANEOUS

         Section 4.01 Effectiveness. This Third Supplemental Indenture shall
become effective upon its execution and delivery by the Company and the Trustee.
Upon the execution and delivery of this Third Supplemental Indenture by the
Company and the Trustee, the Indenture shall be supplemented in accordance
herewith, and this Third Supplemental Indenture shall form a part of the
Indenture for all purposes, and every Holder of Securities heretofore or
hereafter authenticated and delivered under the Indenture shall be bound
thereby.

         Section 4.02 Indenture Remains in Full Force and Effect. Except as
supplemented hereby, all provisions in the Indenture shall remain in full force
and effect.

         Section 4.03 Indenture and Third Supplemental Indenture Construed
Together. This Third Supplemental Indenture is an indenture supplemental to and
in implementation of the Indenture, and the Indenture and this Third
Supplemental Indenture shall henceforth be read and construed together.

         Section 4.04 Confirmation and Preservation of Indenture. The Indenture
as supplemented by this Third Supplemental Indenture is in all respects
confirmed and preserved.

         Section 4.05 Conflict with Trust Indenture Act. If any provision of
this Third Supplemental Indenture limits, qualifies or conflicts with any
provision of the Trust Indenture Act of 1939, as amended (the "Trust Indenture
Act"), that is required under the Trust Indenture Act to be part of and govern
any provision of this Third Supplemental Indenture, the provision of the Trust
Indenture Act shall control. If any provision of this Third Supplemental
Indenture modifies or excludes any provision of the Trust Indenture Act that may
be so modified or excluded, the provision of the Trust Indenture Act shall be
deemed to apply to the Indenture as so modified or to be excluded by this Third
Supplemental Indenture, as the case may be.

         Section 4.06 Severability. In case any provision in this Third
Supplemental Indenture shall be invalid, illegal or unenforceable, the validity,
legality and enforceability of the remaining provisions shall not in any way be
affected or impaired thereby.

         Section 4.07 Headings. The Article and Section headings of this Third
Supplemental Indenture have been inserted for convenience of reference only, are
not to be considered a part of this Third Supplemental Indenture and shall in no
way modify or restrict any of the terms or provisions hereof.

         Section 4.08 Benefits of Third Supplemental Indenture, etc. Nothing in
this Third Supplemental Indenture or the Securities, express or implied, shall
give to any Person, other than the parties hereto and thereto and their
successors hereunder and thereunder and the Holders of the Securities, any
benefit of any legal or equitable right, remedy or claim under the Indenture,
this Third Supplemental Indenture or the Securities.

         Section 4.09 Successors. All agreements of the Company in this Third
Supplemental Indenture shall bind its successors. All agreements of the Trustee
in this Third Supplemental Indenture shall bind its successors.

         Section 4.10 Trustee Not Responsible for Recitals. The recitals
contained herein shall be taken as the statements of the Company and the Trustee
assumes no responsibility for their correctness.


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The Trustee shall not be liable or responsible for the validity or sufficiency
of this Third Supplemental Indenture.

         Section 4.11 Certain Duties and Responsibilities of the Trustee. In
entering into this Third Supplemental Indenture, the Trustee shall be entitled
to the benefit of every provision of the Indenture relating to the conduct or
affecting the liability or affording protection to the Trustee, whether or not
elsewhere herein so provided.

         Section 4.12 Governing Law. THE LAWS OF THE STATE OF NEW YORK SHALL
GOVERN THIS third SUPPLEMENTAL INDENTURE WITHOUT REGARD TO PRINCIPLES OF
CONFLICTS OF LAWS, WHICH would require the application of the laws of another
jurisdiction.

         Section 4.13 Counterpart Originals. The Company and the Trustee may
sign any number of copies of this Third Supplemental Indenture. Each signed copy
shall be an original, but all of them together represent the same agreement.


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                  IN WITNESS WHEREOF, the parties hereto have caused this Third
Supplemental Indenture to be duly executed, all as of the date and year first
above written.


                                       SIRIUS SATELLITE RADIO INC.


                                       By:     /s/ Patrick Donnelly
                                          --------------------------------------
                                          Name:  Patrick Donnelly
                                          Title: Executive Vice President,
                                                 General Counsel and Secretary


                                       HSBC BANK USA, as Trustee


                                       By:     /s/ Robert Conrad
                                          --------------------------------------
                                          Name:   Robert A. Conrad
                                          Title:  Vice President


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Source: OneCLE Business Contracts.